Glioblastoma multiforme (GBM) is a malignant primary brain tumour with an incidence of 1 to 2 per 100 000 population in Hong Kong.1 The survival of patients with GBM remains dismal, mainly due to its inevitable progression and recurrence. Little progress was made until the last decade. The establishment of concomitant chemoradiotherapy (CCRT) with temozolomide (TMZ) and the discovery of O⁶-methylguanine-DNA methyltransferase (MGMT) promoter methylation in association with significantly better outcome were the two major and inspiring breakthroughs.2 3 Before these developments, the treatment for GBM was homogeneous but desperate, and comprised surgery and irradiation only.

In 2001, TMZ was first used in the treatment of recurrent high-grade glioma in Hong Kong. Its favourable anti-tumour activity and acceptable safety profile were proven in a local study.4 In 2005, TMZ was the first chemotherapy to show objective survival benefit as a primary treatment when used together with radiotherapy as part of CCRT in GBM.2 Since then, CCRT for GBM has become the norm in Hong Kong.

In the last decade, opinion has changed about the goal of surgical resection in treating glioma. Ample evidence has shown that maximum safe resection in GBM improves survival. Neurosurgeons have therefore revised their objective of surgery from a diagnostic biopsy or limited debulking to a maximum safe resection. Knowing the infiltrative nature of the tumour, surgeons have a demanding job of balancing maximum resection and safe surgery. Awake craniotomy and mapping technique are two essential surgical techniques that enable safe resection.5 The goal of maximum resection can be achieved with a fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA).6

Given these changes to the management of GBM, we therefore analysed the changes in overall survival of GBM over the past 10 years in Hong Kong.

Data were retrieved from the Chinese University of Hong Kong Otto Wong Brain Tumour Centre brain tumour registry. The registry has been collecting data from all histology-proven glioma patients in the institute since January 2003. Patients aged 18 years or above with histologically proven glioma diagnosed in the institute were included in the registry. Patients with histologically confirmed World Health Organization grade IV GBM during January 2003 to December 2005 and January 2010 to December 2012 were recruited and grouped. Patients treated between 2006 and 2009 were excluded because the surgical policy was evolving and the availability of chemotherapy was variable during the period. Therefore this would be a heterogeneous group of patients with various treatments due to availability or affordability. Patients with an unstable neurological condition or who were considered a poor medical risk after surgery resulting in Karnofsky Performance Scale score of below 70 were excluded, as were those who received initial chemotherapeutics other than TMZ, ie procarbazine, lomustine, vincristine, or bevacizumab. Data on type of surgery, extent of resection, tumour histology, irradiation and chemotherapy parameters were collected as well as information about patient’s age and gender. The registry defined the death date according to the electronic patient record in the Hospital Authority Clinical Management System. For patients who defaulted from clinical follow-up, telephone follow-up ascertained death date. The study end date was 30 June 2015.

During 2003 to 2005, all patients were treated with surgical resection and adjuvant radiotherapy; TMZ was only used in patients with recurrent disease. Ability to pay for chemotherapy was the key determinant of its application and utility. In our hospital, TMZ was prescribed at a dose of 200 mg/m² once per day for 5 days in a 28-day cycle.

With regard to the contouring methodology of irradiation, either European Organisation for Research and Treatment of Cancer or Radiation Therapy Oncology Group protocol was chosen according to the serial assessment of both pre- and post-operative magnetic resonance imaging (MRI) scans. A total dose of 60 Gy irradiation was delivered to the tumour bed and its adjacent tissue in 30 fractions, with 2 Gy each.

Since 2009, neuroradiologists have been responsible for assessing the extent of resection by MRI on postoperative day 1. Total resection was defined as no remaining contrast enhancement on MRI T1-weighted and subtraction scans of T1 plain with T1 plus contrast. For patients in whom the enhancing lesion was still noticeable, the resection was categorised as debulking.

In the 2010-2012 cohorts, TMZ was recommended to all patients. The dosage was 75 mg/m²/day concomitant with radiotherapy, then 150-200 mg/m²/day on the first 5 days every 4 weeks for 6 cycles, in accordance with the regimen described by Stupp et al.2 Methylation status of the MGMT was detected using methylation-specific polymerase chain reaction at our institution. The method has been explained in detail in one of our earlier studies.7 Survival was calculated from the date of surgery for brain tumour to death. Kaplan-Meier survival curves were used to compare different groups of biopsy versus surgical resection and chemoradiotherapy versus radiotherapy alone.

This audit review was done in accordance with the principles outlined in the Declaration of Helsinki.

Demographics, management, and survival of patients are shown in the Table.

During the period 1 January 2003 to 31 December 2005, 26 patients with a mean age of 52.2 years were eligible for study. Two patients below the age of 18 years were excluded from the registry. The median overall survival for this cohort was 7.4 months (Fig 1). Eight (30.7%) patients underwent biopsy only, with a non-inferior median overall survival compared with the remaining 18 patients who underwent resection (7.2 months vs 7.4 months, P=0.988, log-rank test; Fig 2). Total removal could be achieved in only two patients, with overall survival of 14.7 and 28.8 months, respectively. For the remaining 16 patients who underwent debulking surgery, the median overall survival was 7.2 months.

During the period 1 January 2010 to 31 December 2012, 42 patients with a mean age of 55.1 years were identified. One patient was excluded because he declined CCRT after surgery and opted for alternative medicine. The median overall survival was markedly prolonged to 12.7 months (P<0.001, log-rank test; Fig 1). The proportion of patients who had biopsy (9/42, 21.4%) during 2010 to 2012 remained similar to 10 years ago (8/26, 30.8%). Patients with resection performed was not significantly different between the two periods (P=0.404, Chi squared test). Overall survival of the surgical resection group was distinctly longer than that for the biopsy group (15.2 months and 4.5 months, respectively; P=0.026, log-rank test; Fig 3). A higher proportion of patients achieved total surgical removal in 2010-2012 than in 2003-2005, being 35.7% (15/42) and 7.7% (2/26), respectively (P=0.015, Chi squared test). The difference between debulking and total resection remained undefined in the 2010-2012 arm (13.0 months vs 16.0 months; P=0.966, log-rank test) by the time of analysis.

Of the 42 patients with GBM during 2010-2012, CCRT was initiated in 23, accompanied by a meaningful longer median survival of 17.9 months compared with only 4.5 months for those given radiotherapy only (P=0.001, log-rank test; Fig 4). Data for MGMT were available in 33 patients. The overall survival of 19 patients with methylated MGMT promoter was longer than that of 14 patients with unmethylated MGMT promoter, being 28.4 months and 6.3 months, respectively (P<0.001, log-rank test).

Improvement in 2-year survival was also evident, from 11.5% in the earlier cohort, to 21.4% in the later one.

Glioma has attracted international research interest over the last 20 years in both clinical and laboratory setting. The determination to fight the disease yielded with proven survival benefit of TMZ in recurrent high-grade glioma in 2000.8 A 6-month event-free survival of 21% in TMZ compared favourably with 9% for procarbazine.8 The full effect of TMZ was reported in a randomised trial as primary treatment for GBM in 2005.2 The regimen included two phases of TMZ, starting with a concomitant phase of daily low-dose TMZ during the course of radiotherapy, followed by the adjuvant phase of a high-dose TMZ for 5 days during each 28-day cycle for 6 cycles.2 The results of the study benchmarked a standard for chemotherapy in the treatment of GBM. The median survival of 14.6 months in the CCRT arm compared favourably with the 12.1 months of the control radiotherapy-alone arm.2

In Hong Kong, TMZ was first introduced in 2001. Its safety and effect had been tested and reported in a small series of recurrent high-grade glioma.4 The use of CCRT in Hong Kong was also reported with favourable results.9 The overall survival was much improved in these 10 years from 7.4 months in 2003-2005 to 12.7 months in 2010-2012. Among the cohorts in 2010-2012, however, only 54.8% (23/42) received CCRT. This can be attributed to the fact that in 2010, TMZ, whilst already incorporated into the Hospital Authority Drug Formulary, was listed as a self-financed item only. The financial burden on patients was the major cause of low usage during the time.

In 2011, TMZ was granted conditional funding through the Samaritan Fund scheme. Approval of funding was based on the financial situation of the patient and the tumour’s MGMT methylation status, with approval only granted to patients with tumours with MGMT methylation. This may have been a cost-effectiveness consideration because the largest survival benefit would be in MGMT-methylated GBM. Local data showed that only 43% of local GBM were methylated in MGMT status,9 thus essentially limiting the possibility of funding for less than half of the patients with GBM. Thus, within the 2010-2012 cohort, only patients diagnosed from 2011 onwards with tumours of methylated MGMT status (accounting for roughly a further half of the patient population) would have benefited from the scheme. This may account for the relatively low number of patients treated with CCRT. Then the policy of restricting funding based on MGMT status was re-addressed and such criterion was removed in 2013. Currently, support of Samaritan Fund for TMZ is available for eligible patients with GBM based on their financial situation, and regardless of their tumour MGMT status.

The treatment of CCRT had made an impact not only on clinical outcomes, but also on the working dynamics between different professional disciplines involved in the management of patients with GBM. The need for timely arrangement and administration of radiotherapy and chemotherapy within a short postoperative window has encouraged a multidisciplinary team approach. This continues to be the current treatment delivery model for patients with GBM in many hospitals in Hong Kong. Better clinical outcomes encouraged professional enthusiasm. In this atmosphere, a local group of clinicians got together and founded the Hong Kong Neuro-Oncology Society in 2011.

The reasons for longer survival of GBM in recent years are likely to be multifactorial. The extent of surgical resection has been intensely studied over the last two decades. Nonetheless, since a prospective randomised surgical study would be unethical, evidence to support maximum safe resection must be gleaned retrospectively. Despite this, neurosurgical professionals were convinced that surgical resection was the first and major treatment for GBM. Surgical conservatism was abandoned and the demand for maximum safe resection was set out by neurosurgeons. This change was reflected in the decrease in surgical biopsy rate from 30.8% in 2003-2005 to 21.4% in 2010-2012. The ability of total surgical removal of the contrast-enhancing tumour was also increased from 7.7% in 2003-2005 to 35.7% in 2010-2012. Local neurosurgeons have been equipped with two surgical techniques to achieve maximum safe resection in the last 10 years—the technique of cortical mapping and awake surgery was brought to all local neurosurgeons in two workshops of commissioned training organised by the Hospital Authority in 2003 and 2010. This technique allows safer resection of the tumour at or near the eloquent area of the brain. A tumour fluorescent technique (5-ALA) was introduced in 2009 that facilitated detection of residual tumour for maximum resection. In 2003-2005, the survival of the surgical resection group and biopsy group was similar but in 2010-2012, those in the surgical resection group survived longer. The difference was probably due to both aggressive surgical resection and CCRT in the latter group.

The major limitation of this study was the presence of potential confounding factors during the 10-year study period. Such factors included incomplete data of MGMT methylation status and extent of resection in the 2003-2005 group. There was no MGMT methylation testing or day-1 MRI scan after resection in 2003-2005. The interval between surgery and commencement of radiotherapy has been controlled to within 4 weeks since 2009 but this was not the case in 2003-2005. All these confounding factors made valid comparison of the effect of surgical resection or chemotherapy during these two time periods difficult. Moreover, the registry included only surgical patients who had undergone biopsy or resection, and excluded a small group of patients, who were usually elderly (age >70 years) or with poor co-morbidities, who may have received radiotherapy or chemotherapy alone.

Hong Kong has made substantial improvements in the management of GBM with improved survival over the last decade. The combination of aggressive surgical strategy and CCRT are probably the driving force for the improvement.

None of the authors has disclosed any conflicts of interest.

1. Pu JK, Ng GK, Leung GK, Wong CK. One-year review of the incidence of brain tumours in Hong Kong Chinese patients as part of the Hong Kong Brain and Spinal Tumours Registry. Surg Pract 2012;16:133-6. Crossref

2. Stupp R, Mason WP, van den Bent MJ, et al. Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med 2005;352:987-96. Crossref

3. Hegi ME, Diserens AC, Gorlia T, et al. MGMT gene silencing and benefit from temozolomide in glioblastoma. N Engl J Med 2005;352:997-1003. Crossref

4. Chan DT, Poon WS, Chan YL, Ng HK. Temozolomide in the treatment of recurrent malignant glioma in Chinese patients. Hong Kong Med J 2005;11:452-6.

5. Chan DT, Kan PK, Lam JM, et al. Cerebral motor cortical mapping: awake procedure is preferable to general anaesthesia. Surg Pract 2010;14:12-8. Crossref

6. Stummer W, Pichlmeier U, Meinel T, et al. Fluorescence-guided surgery with 5-aminolevulinic acid for resection of malignant glioma: a randomised controlled multicentre phase III trial. Lancet Oncol 2006;7:392-401. Crossref

7. Dong SM, Pang JC, Poon WS, et al. Concurrent hypermethylation of multiple genes is associated with grade of oligodendroglial tumors. J Neuropathol Exp Neurol 2001;60:808-16. Crossref

8. Yung WK, Albright RE, Olson J, et al. A phase II study of temozolomide vs. procarbazine in patients with glioblastoma multiforme at first relapse. Br J Cancer 2000;83:588-93. Crossref

9. Chan DT, Kam MK, Ma BB, et al. Association of molecular marker O⁶Methylguanine DNA methyltransferase and concomitant chemoradiotherapy with survival in Southern Chinese glioblastoma patients. Hong Kong Med J 2011;17:184-8.

A video clip showing management of traumatic patellar dislocation is available at www.hkmj.org

Patellar dislocation is a common injury in young, active individuals and accounts for approximately 3% of all knee injuries. The overall incidence is about 1 in 1000.1 2 Without appropriate treatment, these injuries may result in significant morbidity, including significant limitations in activity and patellofemoral arthritis.3 4 The management of patellar dislocation must take into account numerous clinical factors including the number of dislocations, chronicity of the dislocation, bony alignment, and status of the articular cartilage.

The management of acute first-time patellar dislocators is controversial. Traditionally, these patients have been managed conservatively but the results of such treatment are highly variable and unpredictable. The recurrent instability rate following conservative treatment in these patients has been reported to be between 17% and 44%.1 5 Limitation of strenuous activity after conservative treatment was reported in 58% of these patients, and failure to return to sports activity in 55%.4 Therefore some authors have recommended early primary surgical stabilisation for this group of patients.3 6 7 Surgery is also indicated in patients who have concomitant osteochondral fractures.8

The management of recurrent patellar dislocators is less controversial. Studies have shown that in patients who have had two dislocations, the risk of further dislocation is as high as 50%.1 Most surgeons would recommend surgical stabilisation for these patients.

The aim of this study was to review and document the short-term results of management of patients with traumatic patellar dislocations in our institute, which is a university hospital that serves as a tertiary and quaternary referral centre in Hong Kong.

Patients with patellar dislocation who were seen in our institution from January 2011 to April 2014 were included in the current study. All patients were cared for according to the institution’s patellar dislocation management algorithm (Fig).

Patients followed up for less than 1 year were excluded from the study. Those who had chronic dislocations (persistent dislocation for more than 6 weeks’ duration) and a history of patellar surgery or osteochondral fracture detected on X-ray were also excluded.

The patellar dislocation management algorithm used in our institution is as follows. Patients are first categorised as first-time dislocators or recurrent dislocators. First-time dislocators are further subcategorised as an acute dislocator or subacute dislocator according to the time interval between presentation and time of injury. If this time interval is 3 weeks or less, they are considered acute dislocators; if more than 3 weeks, they are subcategorised as subacute dislocators.

For first-time acute dislocators, medial patellofemoral ligament (MPFL) repair surgery is advised. Preoperative magnetic resonance imaging (MRI) is not routinely performed. The exact site of MPFL tear is identified intra-operatively by combining knee arthroscopy and MPFL endoscopy. If the MPFL is found avulsed at the femoral origin or patellar insertion, it is repaired to bone using suture anchors. If the MPFL is torn at mid-substance, a direct end-to-end repair is performed. Minimal plication of the medial retinaculum was observed in all our cases. A hinged knee brace from full extension to 20-degree flexion is applied for 3 weeks, followed by patellar stabilisation orthosis for another 3 weeks. Supervised physiotherapy in terms of quadriceps strengthening exercises, range of motion training, and patellar mobilisation exercises is offered for 3 to 6 months and the patient is also advised to avoid pivoting sports for at least 6 months.

For first-time subacute dislocators, conservative treatment is offered. This includes wearing of a patellar stabilisation orthosis for a total of 6 weeks after the dislocation and a period of supervised physiotherapy (focusing on quadriceps strengthening exercises and range of motion training) for at least 6 weeks to 3 months. Patients are advised to avoid any pivoting sports for a total of 6 months. A similar regimen of conservative treatment is offered to those first-time acute dislocators who refuse surgical intervention. The whole course of rehabilitation usually lasts 4 to 6 months before the patient is permitted to resume full activity.

For recurrent dislocators, patients are advised to have MPFL reconstruction. Plain computed tomography of the knee is performed to measure the tibial tubercle–trochlear groove (TT-TG) distance. If this distance measures ≤20 mm, MPFL reconstruction surgery is advised. If this distance measures >20 mm, MPFL reconstruction and tibial tubercle osteotomy surgery for anteromedialisation of the tibial tubercle are advised. The rehabilitation protocol following MPFL reconstruction is the same as that for MPFL repair. For recurrent dislocators who refuse surgery, conservative treatment is advised. This consists of a 3- to 6-month course of supervised physiotherapy.

The following outcome measures were recorded before treatment and 1 year after treatment in our study patients: (1) International Knee Documentation Committee (IKDC) score; (2) Tegner activity level scale score; and (3) presence of apprehension sign on physical examination. The redislocation rate at 1 year after treatment was also measured for the different groups of treatment.

The IKDC score is a knee-specific self-evaluation score for reporting patient symptoms, function, and sports activity.9 Tegner activity level scale score is a functional score describing a patient’s activity level.10 The presence of apprehension sign was documented by one of the two observers, who were experienced sports surgeons in the authors’ institute. The test was performed with the patient lying supine on the examination couch. The knee was passively flexed to 20 degrees. A lateral displacing force was applied manually on the medial side of patella in an attempt to sublux the patella laterally. Apprehension sign was defined as positive if the patient reported a sense of subluxation or attempted to stop the examiner.

Data were analysed and compared with the Statistical Package for the Social Sciences (Windows version 23.0; SPSS Inc, Chicago [IL], US). The Wilcoxon signed-rank test (non-parametric, paired samples test) was used to compare IKDC score and Tegner activity level scale results before and after treatment within the same treatment group. The McNemar test (non-parametric, paired samples test) was used to compare the percentage of patients with apprehension sign before and after treatment within the same treatment group. The Mann-Whitney U test (non-parametric, independent samples test) was used to compare IKDC score as well as Tegner activity level scale results between conservative treatment group and surgery group. The Pearson’s Chi squared test (non-parametric, independent samples test) was used to compare the percentage of patients with apprehension sign as well as recurrent dislocation rate between conservative treatment group and surgery group. Whenever expected counts were less than five, Fisher’s exact test was used instead of Pearson’s Chi squared test. This study was done in accordance with the principles outlined in the Declaration of Helsinki.

A total of 81 patients were identified. Of these, 40 patients were excluded—27 were excluded due to follow-up of less than 1 year, six due to osteochondral injury detected by X-ray, three due to chronic dislocation, two due to development of patellofemoral osteoarthritis, and two due to a history of patellar surgery (Table 1). This left us with 41 patients comprising 17 males and 24 females. Their mean age was 23.6 years (range, 13-44; standard deviation, 7.4 years). A summary of patient demographics is shown in Table 2.

There were 20 patients who were first-time dislocators and 21 patients who were recurrent dislocators. Among the first-time dislocators (n=20), 45% (n=9) were treated conservatively and 55% (n=11) were treated with MPFL repair surgery. Among the recurrent dislocators, 33% (n=7) were treated conservatively, 62% (n=13) were treated with MPFL reconstruction surgery, and 5% (n=1) were treated with combined tibial tubercle osteotomy and MPFL reconstruction surgery. Their results are summarised in Table 3.

Among the first-time dislocators who received conservative treatment (n=9), recurrent dislocation occurred in 33% (n=3) within 1 year of treatment. The findings are shown in Table 3. There were no statistically significant differences between the Tegner activity level scale or percentage of patients with apprehension sign before and 1 year after treatment.

Among the first-time dislocators who underwent MPFL repair surgery (n=11), intra-operative MPFL exploration showed 55% (n=6) of them had tears at the patellar insertion, 27% (n=3) had MPFL tear at the femoral origin, and 18% (n=2) had MPFL mid-substance tear (one of which was only a partial mid-substance tear). Preoperative MRI was performed in seven of the 11 patients. Among six of these seven patients, MPFL detected on preoperative MRI correlated with the tear site on intra-operative MPFL exploration. In the remaining patient, only a partial tear of MPFL at mid-substance was found intra-operatively; this was not detected by the preoperative MRI. Regarding the outcome of surgery, there were no recurrent dislocations within 1 year of surgery (Table 3). Apprehension sign was present in 88% before surgery and 9% 1 year after surgery (P=0.07, McNemar test). There were no statistically significant differences between the Tegner activity level scale or percentage of patients with apprehension sign before and 1 year after surgery.

Comparison of first-time dislocators who received conservative treatment with first-time dislocators who underwent MPFL repair surgery 1 year after treatment revealed no significant difference in IKDC score. There was a lower percentage of patients with apprehension sign (9% vs 33%) and a lower rate of redislocation in the MPFL repair surgery group (0% vs 33%, P=0.07, Fisher’s exact test) but the differences were not statistically significant.

Among the recurrent dislocators who received conservative treatment (n=7), recurrent dislocation occurred in 71% (n=5) of patients within 1 year of treatment (Table 3). Apprehension sign was present in 14% before treatment and 29% 1 year after treatment. There was no statistically significant difference between the IKDC score, Tegner activity level scale, or percentage of patients with apprehension sign before and 1 year after treatment.

Among the recurrent dislocators who underwent MPFL reconstruction surgery (n=13), there were no recurrent dislocations within 1 year of surgery (Table 3). Apprehension sign was present in 62% before surgery and no patients had apprehension sign 1 year after surgery. There were statistically significant improvements in the IKDC score (P=0.02, Wilcoxon signed-rank test), Tegner activity level scale score (P=0.04, Wilcoxon signed-rank test), as well as percentage of patients with apprehension sign (P<0.01, McNemar test).

One year after treatment, comparison of recurrent dislocators who received conservative treatment with recurrent dislocators who underwent MPFL reconstruction surgery revealed that the mean IKDC score was significantly better in the MPFL reconstruction surgery group (80.0 vs 67.7; P=0.02, Mann-Whitney U test). The redislocation rate was significantly lower in the MPFL reconstruction surgery group (0% vs 71%; P<0.01, Fisher’s exact test). There was a lower percentage of patients with apprehension sign in the MPFL reconstruction surgery group (0% vs 29%) although the difference was not statistically significant.

For acute first-time patellar dislocators, it has been widely agreed that in the presence of concomitant osteochondral fracture, surgical treatment is indicated.11 The indication of surgery for acute first-time patellar dislocators without osteochondral fractures is controversial. The recurrent instability rate after conservative treatment in these patients has been reported to be 17% to 44%.1 5 It has traditionally been held that these patients should be treated conservatively.11 Nine prospective randomised controlled trials have compared conservative and surgical treatment in first-time dislocators and the results have been inconsistent.12 13 14 15 16 17 18 19 20 In their systematic review, Stefancin and Parker11 recommended conservative treatment for most patients after first-time dislocation, except those with concomitant osteochondral fracture and those with significant medial soft tissue damage who may benefit more from surgical treatment. Smith et al21 reviewed 11 studies that included five randomised controlled trials. They found that surgical treatment of patellar dislocation was associated with a significantly higher risk of patellofemoral joint osteoarthritis but a significantly lower risk of subsequent patellar dislocation compared with conservative treatment.21 A recent Cochrane review of six studies with 344 participants found that participants managed surgically had a significantly lower risk of recurrent dislocation following first-time dislocation at 2 to 9 years of follow-up compared with those managed conservatively.22 There were no differences in physical function scores. The authors, however, pointed out that the quality of evidence was very low because of the high risk of bias and the imprecision of the effect estimates.22 They recommended that adequately powered, multicentre, randomised controlled trials are needed to substantiate this evidence.22 Erickson et al23 carried out a systematic review of four meta-analyses on surgical treatment of first-time patellar dislocations. Three meta-analyses showed a lower subsequent patellar dislocation rate in first-time dislocators managed surgically compared with those managed conservatively, whereas one meta-analysis did not show any difference in redislocation rates. Using the combined results of all studies, the overall recurrent dislocation rate was 24% in the surgery group and 34.6% in the conservative treatment group. One meta-analysis found a significantly higher rate of patellofemoral osteoarthritis in the surgery group. There were no differences in functional outcome scores between the conservative treatment group and surgery group.23 Our study showed that conservative treatment and surgical treatment were both effective in restoring knee function at 1-year follow-up. Nonetheless there was a trend towards a lower rate of redislocation in the MPFL repair surgery group, although it did not reach statistical significance. This suggests that operative treatment may be more beneficial for this group of patients.

In the current study, for first-time dislocators with delayed presentation of more than 3 weeks, conservative treatment was advised. This was because a certain degree of healing of the torn MPFL in the elongated position with a variable amount of scar tissue in the gap was anticipated if the patient presented subacutely. As the operative protocol of direct repair of MPFL was adopted in this study, the presence of partial healing in an elongated position affects the decision of correct tension in the MPFL during direct repair. As a result, a conservative approach was adopted to minimise the possibility of overtensioning (which might lead to medial patellofemoral joint pain) or undertensioning (which might lead to recurrent instability).

For recurrent patellar dislocators, studies have shown a redislocation rate of up to 50%.1 Therefore, it has been widely agreed that recurrent dislocation is a strong indication for surgical treatment.24 Reconstruction of MPFL, tibial tubercle osteotomy, and trochleoplasty have all been well-described surgical procedures for management of recurrent patellar dislocators. Reconstruction of MPFL alone is indicated in the presence of a physiological TT-TG distance (<20 mm) and no significant trochlear dysplasia.25 Patients with increased TT-TG distance of >15 to 20 mm have been shown to have patellar instability.26 Thus, tibial tubercle osteotomy procedures, aiming to shift the tibial tubercle medially to correct the TT-TG distance to within physiological limits of around 9 to 15 mm, with or without concomitant MPFL reconstruction have been advocated for these patients.25 The cut-off point of 20 mm above which tibial tubercle osteotomy is indicated has been well accepted by most orthopaedic surgeons.26 27 28 29 30 One study has shown that 18% of recurrent patellar dislocators had TT-TG distances of >20 mm.31 For patients with significant trochlear dysplasia, trochleoplasty procedures have been advocated.25 There have been no prospective randomised controlled trials to date comparing conservative treatment and the various surgical treatment modalities for recurrent patellar dislocators. Short-term results of these various surgical procedures have been satisfactory, however. Our study demonstrated similar results to the current literature, showing a clear advantage in terms of knee function, return to activity, and apprehension in the MPFL reconstruction surgery group compared with the conservative treatment group.

There are several limitations of this study. First, the sample size was small and a large number of patients were lost to follow-up, making the study underpowered. This was reflected by the non-significant finding in the positive apprehension sign before (88%) and 1 year (9%) after MPFL repair in first-time dislocators (P=0.07, McNemar test). Second, we did not adjust for confounding factors for patellar dislocation, for example, patella alta, increased Q-angle, and ligamentous laxity. Third, one of the outcomes compared (apprehension sign) was highly assessor-dependent. Although the method of detecting apprehension sign was standardised and the number of assessors was limited to two, potential bias could still be introduced. In addition, no inter-observer or intra-observer repeatability tests were carried out. Fourth, the final assessment in the current study was performed at 12-month follow-up. This short follow-up may not allow adequate evaluation of postoperative outcome. Readers of the journal need to be aware of this during extrapolation of the conclusion of the current study to their clinical practice. Lastly, since there was only one recurrent dislocator who underwent tibial tubercle osteotomy, we are unable to conclude the results of this form of treatment.

A management algorithm for patella dislocation is presented. Repair of MPFL reduced the risk of recurrent dislocation in first-time dislocators.

All authors have disclosed no conflicts of interest.

1. Fithian DC, Paxton EW, Stone ML, et al. Epidemiology and natural history of acute patellar dislocation. Am J Sports Med 2004;32:1114-21. Crossref

2. Hsiao M, Owens BD, Burks R, Sturdivant RX, Cameron KL. Incidence of acute traumatic patellar dislocation among active-duty United States military service members. Am J Sports Med 2010;38:1997-2004. Crossref

3. Hawkins RJ, Bell RH, Anisette G. Acute patellar dislocations. The natural history. Am J Sports Med 1986;14:117-20. Crossref

4. Atkin DM, Fithian DC, Marangi KS, Stone ML, Dobson BE, Mendelsohn C. Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury. Am J Sports Med 2000;28:472-9.

5. Cofield RH, Bryan RS. Acute dislocation of the patella: results of conservative treatment. J Trauma 1977;17:526-31. Crossref

6. Sallay PI, Poggi J, Speer KP, Garrett WE. Acute dislocation of the patella. A correlative pathoanatomic study. Am J Sports Med 1996;24:52-60. Crossref

7. Ahmad CS, Stein BE, Matuz D, Henry JH. Immediate surgical repair of the medial patellar stabilizers for acute patellar dislocation. A review of eight cases. Am J Sports Med 2000;28:804-10.

8. Colvin AC, West RV. Patellar instability. J Bone Joint Surg Am 2008;90:2751-62. Crossref

9. Irrgang JJ, Anderson AF, Boland AL, et al. Development and validation of the international knee documentation committee subjective knee form. Am J Sports Med 2001;29:600-13.

10. Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res 1985;(198):43-9. Crossref

11. Stefancin JJ, Parker RD. First-time traumatic patellar dislocation: a systematic review. Clin Orthop Relat Res 2007;455:93-101. Crossref

12. Christiansen SE, Jakobsen BW, Lund B, Lind M. Isolated repair of the medial patellofemoral ligament in primary dislocation of the patella: a prospective randomized study. Arthroscopy 2008;24:881-7. Crossref

13. Bitar AC, Demange MK, D’Elia CO, Camanho GL. Traumatic patellar dislocation: nonoperative treatment compared with MPFL reconstruction using patellar tendon. Am J Sports Med 2012;40:114-22. Crossref

14. Camanho GL, Viegas Ade C, Bitar AC, Demange MK, Hernandez AJ. Conservative versus surgical treatment for repair of the medial patellofemoral ligament in acute dislocations of the patella. Arthroscopy 2009;25:620-5. Crossref

15. Nikku R, Nietosvaara Y, Aalto K, Kallio PE. Operative treatment of primary patellar dislocation does not improve medium-term outcome: A 7-year follow-up report and risk analysis of 127 randomized patients. Acta Orthop 2005;76:699-704. Crossref

16. Nikku R, Nietosvaara Y, Kallio PE, Aalto K, Michelsson JE. Operative versus closed treatment of primary dislocation of the patella. Similar 2-year results in 125 randomized patients. Acta Orthop Scand 1997;68:419-23. Crossref

17. Palmu S, Kallio PE, Donell ST, Helenius I, Nietosvaara Y. Acute patellar dislocation in children and adolescents: a randomized clinical trial. J Bone Joint Surg Am 2008;90:463-70. Crossref

18. Sillanpää PJ, Mäenpää HM, Mattila VM, Visuri T, Pihlajamäki H. Arthroscopic surgery for primary traumatic patellar dislocation: a prospective, nonrandomized study comparing patients treated with and without acute arthroscopic stabilization with a median 7-year follow-up. Am J Sports Med 2008;36:2301-9. Crossref

19. Sillanpää PJ, Mattila VM, Mäenpää H, Kiuru M, Visuri T, Pihlajamäki H. Treatment with and without initial stabilizing surgery for primary traumatic patellar dislocation. A prospective randomized study. J Bone Joint Surg Am 2009;91:263-73. Crossref

20. Petri M, Liodakis E, Hofmeister M, et al. Operative vs conservative treatment of traumatic patellar dislocation: results of a prospective randomized controlled clinical trial. Arch Orthop Trauma Surg 2013;133:209-13. Crossref

21. Smith TO, Song F, Donell ST, Hing CB. Operative versus non-operative management of patellar dislocation. A meta-analysis. Knee Surg Sports Traumatol Arthrosc 2011;19:988-98. Crossref

22. Smith TO, Donell S, Song F, Hing CB. Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database Syst Rev 2015;(2):CD008106. Crossref

23. Erickson BJ, Mascarenhas R, Sayegh ET, et al. Does operative treatment of first-time patellar dislocations lead to increased patellofemoral stability? A systematic review of overlapping meta-analyses. Arthroscopy 2015;31:1207-15. Crossref

24. Koh JL, Stewart C. Patellar instability. Orthop Clin North Am 2015;46:147-57. CrossRef

25. Petri M, Ettinger M, Stuebig T, et al. Current concepts for patellar dislocation. Arch Trauma Res 2015;4:e29301. Crossref

26. Dejour H, Walch G, Nove-Josserand L, Guier C. Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 1994;2:19-26. Crossref

27. Drexler M, Dwyer T, Dolkart O, et al. Tibial rotational osteotomy and distal tuberosity transfer for patella subluxation secondary to excessive external tibial torsion: surgical technique and clinical outcome. Knee Surg Sports Traumatol Arthrosc 2014;22:2682-9. Crossref

28. Paulos L, Swanson SC, Stoddard GJ, Barber-Westin S. Surgical correction of limb malalignment for instability of the patella: a comparison of 2 techniques. Am J Sports Med 2009;37:1288-300. Crossref

29. Pandit S, Frampton C, Stoddart J, Lynskey T. Magnetic resonance imaging assessment of tibial tuberosity–trochlear groove distance: normal values for males and females. Int Orthop 2011;35:1799-803. Crossref

30. Alemparte J, Ekdahl M, Burnier L, et al. Patellofemoral evaluation with radiographs and computed tomography scans in 60 knees of asymptomatic subjects. Arthroscopy 2007;23:170-7. Crossref

31. Köhlitz T, Scheffler S, Jung T, et al. Prevalence and patterns of anatomical risk factors in patients after patellar dislocation: a case control study using MRI. Eur Radiol 2013;23:1067-74. Crossref

Fragile X syndrome (FXS) is the second leading genetic cause of intellectual disability after Down syndrome,1 affecting one in 4000 males and one in 8000 females.2 The typical phenotypes include behavioural abnormalities, autism, cognitive impairment, and dysmorphism such as large protruding ears, elongated face, and macroorchidism in male patients. This syndrome is caused by a defective fragile X mental retardation 1 (FMR1) gene located on the X chromosome, where there is an unstable cytosine-guanine-guanine (CGG) trinucleotide repeat in the 5’ untranslated region.3 Normally the number of CGG repeats is less than 44, but if it is more than 200 (full mutation), the FMR1 gene expression will be ‘shut down’ due to methylation of its promoter. The protein product, which is essential for normal neurodevelopment, is thus not produced. When the repeat number is between 55 and 200 (pre-mutation),4 the FMR1 gene can be expressed but the repeat number is potentially expandable to full mutation during its transmission to the next generation. Such risk of expansion is increased with the size of the repeat number, and is close to 100% when the size of CGG repeats is 100 or more. In addition, pre-mutation carriers are at risk of developing fragile X–associated primary ovarian insufficiency (FXPOI) and fragile X–associated tremor/ataxia syndrome (FXTAS) in late adult life, although they are mentally normal.5 6 Intermediate alleles are repeat numbers between 45 and 54, and individuals carrying theses alleles are at risk of expanding into pre-mutation but not into full mutation.7 8 9

Because of the significant morbidity associated with FXS, and since most maternal carriers are clinically silent during their reproductive years, many experts have put forward the notion of preconception or prenatal fragile X carrier screening for females.10 The prevalence of pre-mutation carriers will directly affect the efficacy and cost-effectiveness of screening, but this varies widely between different ethnic groups and countries. While it is well known that Caucasians and Jews have high carrier rates of 1 in 100-250,10 many studies in Chinese populations report an extremely low carrier rate.11 12 13 Among these studies, the largest included 10 046 newborn boys, but identified only six pre-mutation carriers (1 in 1674).13 These studies, however, were limited by the fact that the screening methods used were polymerase chain reaction (PCR) assays that were not accurate or were unable to amplify long CGG repeats.14 In addition, the screening of a low-risk Chinese pregnant population has not been studied.

Recently, we have validated a new fragile-X-related–specific PCR assay that utilises a low-cost capillary electrophoresis instrument and the FragilEase reagent kit (PerkinElmer Inc, Waltham [MA], US), and is able to detect CGG repeat numbers at a level as high as 1000.14 The repeat numbers analysed by this new assay were highly concordant with those obtained from the conventional reference method (PCR + Southern blot) in 112 archived samples, including 25 samples of full mutation (the largest allele size measured at 1380 repeats). The intra-assay (coefficient of variation <2.5%) and inter-assay imprecision was within 1 CGG repeat.14 The objectives of this study were to determine the prevalence of FXS pre-mutation carriers and the distribution of repeat numbers in the Chinese pregnant population in Hong Kong, using this FXS-specific PCR assay.

This was a prospective observational study conducted at a university hospital in Hong Kong between April 2013 and May 2015. Chinese pregnant women between 4 and 41 weeks of gestation, at or above the age of 18 years who could understand English or Chinese and give informed consent were eligible for the study. Eligible women were approached in the antenatal clinic or the antenatal ward by the research assistant at one convenient time-point once per day and invited to participate in the study. Women with a known family history of FXS were excluded to avoid an over-representation of the pre-mutation carrier rate in the general population, so that data obtained would be more useful in determining whether population-based screening is beneficial. Pre-test counselling was given by a research assistant with a bachelor’s and master’s degree in human genetics. Printed information about fragile X carrier testing was provided and included information about the clinical features and maternal inheritance of the disease. It was also explained to participants that genetic counselling would be offered if they were found to have an increased CGG repeat number of ≥45. Testing was entirely voluntary, and no payment was received by the participants. Written informed consent was obtained. Two millilitres of maternal blood was collected in an EDTA tube from each participant. The FMR1 CGG repeat result could be obtained within 1 day but study samples were processed in batches so results were available between 1 day and 7 months later. Women were informed prior to consenting that the result might not be available before delivery.

The FMR1 CGG repeat status of each sample was tested at a screen cut-off value of ≥45.14 The details of the PCR method are described below. All participants had the right to access personal data and study results. Positive test results (≥45 CGG repeats) would be made known to the participants, and genetic counselling would be provided. Where indicated, prenatal and postnatal diagnoses were offered by means of chorionic villus sampling or amniocentesis and cord blood or neonatal blood respectively, with analysis of CGG repeats in the extracted DNA from the sample using the same PCR method.

Approval for the study was obtained from the institutional review board of the Joint-Chinese University of Hong Kong–New Territories East Cluster Clinical Research Ethics Committee (CRE-2013.055).

Genomic DNA was extracted from peripheral blood samples using DNeasy Blood & Tissue Kit according to the manufacturer’s protocol (Qiagen, Hilden, Germany) or using the automatic system, chemagic Prepito-D, following the manufacturer’s protocol (PerkinElmer, Turku, Finland).

The FMR1 repeat region of each DNA sample was amplified using the FragilEase PCR reagent kit following the manufacturer’s protocol (PerkinElmer). It involved a forward (TCA GGC GCT CAG CTC CGT TTC GGT TTC A) and a reverse primer (FAM-AAG CGC CAT TGG AGC CCC GCA CTT CC) anneal to FMR1-specific sequence upstream and downstream of the trinucleotide repeat region, respectively. Thermal cycle amplification of the highly GC-rich trinucleotide repeat region produced fragments whose size was directly related to the number of trinucleotide repeats present in the DNA sample. Two female reference DNA samples (one pre-mutation carrier [30/80 repeats] and one individual with full mutation [20/200 repeats]) for evaluating the analytical performance of the assay were obtained from the Coriell Institute for Medical Research (Camden, US). The known repeat sizes of the reference samples were concurrently amplified and used to calculate the CGG repeat numbers of the unknown samples.

Polymerase chain reaction products were purified using NucleoFast 96 PCR plate (MACHEREY-NAGEL GmbH &amp Co KG, Germany) or the PureLink PCR Micro Kit (Invitrogen, Carlsbad [CA], US). Purification procedures were performed according to the manufacturer’s instructions with a final elution volume of 20 µL.

The fragment size for the sample was analysed using 2100 Bioanalyzer (Agilent Technologies, Santa Clara [CA], US). In this study, 3 µL of the purified PCR product and 3 µL of the 7500-size marker reagent (from an Agilent DNA 7500 kit) were loaded into each of the 12 wells of the Bioanalyzer chip. A standard curve was constructed from the two female reference samples (Coriell NA20240 [30/80 CGG repeats] and NA20239 [20/200 CGG repeats]) with known repeat size. This allowed the determination of CGG repeat size with higher accuracy.

FraXsoft analysis software (PerkinElmer) was used to calculate the CGG repeat lengths by utilising the base pair size data exported from the bioanalyser. Fragment sizes that were below 200 CGG repeats were interpolated from their base-pair electrophoresis result using a linear regression constructed between the four allele values of the two Coriell female reference samples. Larger repeat sizes (>200 repeats) were calculated by extrapolation along the same regression line.14

A convenient sample of 2650 Chinese pregnant women was recruited between 4 and 41 weeks of gestation. FMR1 allelic expansion was screened in each subject, and two pre-mutation carriers (0.08%, one in 1325) and one asymptomatic individual with full mutation (0.04%, one in 2650) who were unrelated were identified. The overall prevalence was therefore one in 883 (0.11%) or 11 per 10 000 (95% confidence interval, 3-36 per 10 000 using the Wilson method with continuity correction). These three women are described in detail below. There were also 30 (1.1%) women with CGG repeats who fell into the intermediate category. The remaining 2617 women screened were found to have normal CGG repeats, and the most common CGG repeat allele was 30. This distribution of allele frequencies for CGG repeats in the FMR1 gene in the population with normal CGG repeat numbers is shown in the Figure.

The woman had FMR1 gene testing carried out during the third trimester and was found to have a full mutation with CGG repeat number of 35/401. She was phenotypically normal. She had completed junior high school education and was working in a fast food restaurant. Upon detailed questioning, she suspected that her brother and one of her maternal male cousins might have some autistic features, but she was not aware of any mental retardation, or any formal genetic diagnosis in either of these two relatives. Genetic counselling was given. Prenatal diagnosis was not performed since the woman had been tested during the third trimester and termination of pregnancy was not an option. She subsequently delivered a healthy baby girl. The parents were counselled about testing the baby for FXS but they declined and preferred to observe the development of their child first. The child was referred for follow-up of her development. The woman’s other family members also declined fragile X screening because they were phenotypically normal with no current reproductive plans.

The first pre-mutation carrier was a 31-year-old nulliparous female with no features associated with FXS or family history of intellectual disability or autism. Testing of the FMR1 gene was done at 13 weeks and 4 days, and the result was available at 14 weeks and 4 days indicating a CGG repeat number of 30/70. The woman requested prenatal diagnosis for her female fetus following genetic counselling. Amniocentesis was performed at gestation 16 weeks and 4 days. The PCR analysis result was available at 17 weeks and 2 days, and revealed that the maternal pre-mutation allele had been transmitted to the fetus and expanded to CGG repeat number of 30/579, indicating the female fetus carried a full-mutation allele. Genetic counselling was provided and the couple opted for termination of pregnancy and planned for pre-implantation genetic diagnosis in future.

The second carrier was a 39-year-old female with normal phenotype and no family history of intellectual disability or autism. She had testing of the FMR1 gene at 20 weeks and 6 days of gestation. The result was available at 21 weeks and 2 days of gestation showing a CGG repeat number of 31/64, and her fetus was female. Following genetic counselling, the parents decided not to have any prenatal or postnatal diagnosis owing to the variable and unpredictable phenotype in full-mutation females.

This is the largest study of the prevalence of fragile X pre-mutation carriers in Chinese pregnant women, as well as the largest one using this new FXS-specific PCR assay (FragilEase) in the Chinese population. The combined prevalence of pre-mutations and full mutations of FXS in normal asymptomatic pregnant Hong Kong Chinese women was as high as 0.11% (1 in 883). We included also one case of full mutation in our estimation of prevalence because some women with full mutations are apparently asymptomatic but are at risk of transmitting FXS to their offspring. Therefore, the combined prevalence would reflect more precisely the overall risk of transmitting FXS in the general population. Our finding is consistent with the recent publication by Huang et al,15 who identified one pre-mutation carrier in their population of 1113 Han Chinese (534 males and 579 non-pregnant females). Our finding also refutes the belief that FXS pre-mutations are extremely rare in Chinese.11 12 13 In fact, the incidence in Chinese is comparable with some of the incidences reported from Korea (1 in 1090).16

A standard capillary analyser is only capable of detecting and sizing FMR1 PCR products with less than 200 CGG repeats. Thus differentiating full mutations with greater than 200 CGG repeats from apparently homozygous normal female samples, and confirming full mutations, has historically required the Southern blot reflex test. The Southern blotting assay, however, is expensive, labour intensive, and requires a large amount of DNA making its use in screening impractical.13 The advantage of this FragilEase PCR assay is the ability to detect up to 1000 CGG repeats, so that even asymptomatic full-mutation individuals can be identified during routine screening, as shown in one of our cases. It has high throughput and high sensitivity of 99%.14 The cost for each fragile X assay is estimated to be only US$44, deduced from a parallel run of a minimum of four samples plus two reference standards on each Bioanalyzer chip, and this cost includes that of FragilEase reagent kit, DNA extraction kit, PCR-related consumables, Bioanalyzer kit, equipment maintenance, and staff costs. Processing of each chip takes 1 hour and a maximum of nine samples per chip can run. The low cost of this test is beneficial as a screening test.

Our study showing an incidence of one pre-mutation or full mutation of FXS in 883 pregnant Chinese women has important implications for counselling and implementation of a FXS carrier screening programme in Hong Kong and in China, as well as in countries where Chinese immigrants are numerous. It remains controversial whether FXS should be screened for, and which model should be adopted. Some experts advocate universal prenatal screening17 as it is much more effective in identification of pre-mutation carriers compared with case finding followed by cascade screening. The latest UK Health Technology Assessment (HTA) review18 indicated that the maximal rate of detection of female pre-mutation carriers by population screening is 60% whereas only 6% of carriers will be identified by active cascade screening. In their simulation model, the additional number of births of FXS children that could be avoided each year was estimated to be 15 with cascade screening compared with 39 with prenatal screening. Since family size tends to be small in many developed countries now, the effectiveness of cascade screening has become very limited. In Hong Kong, the average number of children per household is only 1.24.19 In mainland China, until 2015, families were allowed to have only one child. The chance of revealing a positive family history with affected siblings or close relatives is thus low. Furthermore, even though parents might be planning their second child, the first affected child would not have been diagnosed with FXS if very young. Such diagnosis is particularly difficult and is delayed in Hong Kong, China, or other Asia-Pacific regions where clinical genetic services are inadequate.20 The variable phenotypes of FXS may also be masked by the mixed education levels of the population in different geographical regions. Indeed, the patient in our study who carried a full mutation is a very good example of the limitation of cascade screening with an uncertain family history or without a formal genetic assessment.

Unlike first-trimester combined Down syndrome screening that requires intensive training and effort in ultrasound measurement and a stringent algorithm in risk calculation to achieve a 90% detection rate with a 5% false-positive rate,21 22 23 24 screening for fragile X carriers is relatively simple by a maternal blood test and is thus acceptable to most women. It can also be done before conception. Furthermore, once a carrier is identified, other carriers may be found through family screening. Hence the potential utility of this screening can be profound. In the validation study of FragilEase by Kwok et al,14 78 samples tested positive, of which one was classified as false positive. This sample was tested to have a CGG repeat number of 55 (pre-mutation) by FragilEase whereas Southern blot analysis determined the repeat number to be 53 (intermediate). This gives a false-positive rate of 1.3%. The false-positive result occurred because the CGG repeat number was at the lower limit of the pre-mutation range, such that a difference of 2 repeats led to an intermediate allele being classified in the pre-mutation range. We believe that this false-positive rate is overestimated, as the majority of the pre-mutation carriers do not have a repeat number at this lower limit that could lead to such a false-positive result. Although the positive predictive value calculated was 8.0%, assuming a fragile X pre-mutation carrier prevalence of one in 883, the performance of the test should be better because the positive predictive value was underestimated due to the overestimated false-positive rate.

There are no current data on the health care costs of caring for a FXS patient in Hong Kong or Asia. In the UK, the lifetime cost for each FXS patient is estimated to be UK$380 000 and the HTA model expects population screening to be a cost-effective strategy.18 In fact, it has been shown that health care professionals and families of patients with FXS are in favour of preconception or prenatal screening.25 26 Detection of pre-mutation alleles also offers information about the women’s own health, as they are at increased risk of FXPOI and FXTAS.27 The above factors may affect a woman’s fertility planning and allow informed choices not only in this pregnancy but also subsequent pregnancies.

Despite this, the UK National Screening Committee and the American College of Obstetricians and Gynecologists do not advocate universal screening,28 29 but rather screening in those with a family history of congenital intellectual disability, autism, or premature ovarian failure. There are concerns over the counselling about complex genetic mechanisms and the psychological impact of FXS when population screening is offered. The difficulties in counselling include (1) the variable phenotypes (eg female fetuses with full mutation) associated with FXS, and (2) identification of individuals with pre-mutation allele may lead to anxiety in these individuals because both FXPOI and FXTAS have no specific treatment. Another factor that limits population screening for fragile X is the access to prenatal care and screening, especially in rural areas of mainland China.

The strength of this study lies in its size. It is the largest study of the prevalence of fragile X pre-mutation carriers performed in the Chinese pregnant women. This study also demonstrated the feasibility of this validated FXS-specific PCR-based method (FragilEase) in the Chinese population.14 One limitation is that not all pregnant women were approached for the study and the study participants were recruited by convenient sampling. During the study period, approximately 13 600 Chinese women attended our hospital but only 2650 women were recruited. Women were recruited each day at one convenient time-point by the research assistant in the antenatal ward or clinic. This was not a true random sample and hence has doubtful representativeness. Nonetheless, as the largest obstetric hospital in Hong Kong with participants recruited from both antenatal clinic and obstetric wards, and a large sample size of 2650, we aimed to include a group most typical of the general obstetric population. Another limitation is that our cohort represented mainly the Southern Chinese population and not the entire Chinese population. Despite this, the findings of our study should provide a strong foundation for further large-scale national studies that may benefit our understanding of the carrier frequencies in different parts of China and the Asia-Pacific region. Further studies are also required to look into the different models of carrier screening programmes and their cost-effectiveness in our locale to determine which screening strategy is the most appropriate in the Chinese pregnant population.

The prevalence of pre-mutation and full-mutation alleles altogether in the asymptomatic Southern Chinese population was one in 883, and that for pre-mutation alleles alone was one in 1325. These figures are higher than those reported previously in small-scale studies, and indicate that FXS is a clinical condition not to be overlooked in our locale. Further studies of the prevalence in different areas of Asia may be beneficial to direct future screening strategies.

We would like to thank the research and laboratory staff of the Fetal Medicine Team, Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong. We would also like to thank all the pregnant women and their families who participated in the study.

This work was supported partially by funding from the Hong Kong Obstetrical and Gynaecological Trust Fund. PerkinElmer has supported some of the PCR study reagents, but has no role in the design of the study; collection, analysis, or interpretation of the data; writing, review, or approval of the manuscript; or the decision to submit the manuscript for publication.

1. Sherman S. Epidemiology. In: Hagerman RJ, Silverman AC, editors. Fragile X syndrome: diagnosis, treatment, and research. Baltimore: The Johns Hopkins University Press; 1991: 69-97.

2. Coffee B, Keith K, Albizua I, et al. Incidence of fragile X syndrome by newborn screening for methylated FMR1 DNA. Am J Hum Genet 2009;8:503-14. Crossref

3. Verkerk AJ, Pieretti M, Sutcliffe JS, et al. Identification of a gene (FMR-1) containing a CGG repeat coincident with a breakpoint cluster region exhibiting length variation in fragile X syndrome. Cell 1991;65:905-14. Crossref

4. Kronquist KE, Sherman SL, Spector EB. Clinical significance of tri-nucleotide repeats in fragile X testing: a clarification of American College of Medical Genetics guidelines. Genet Med 2008;10:845-7. Crossref

5. Jacquemont S, Leehey MA, Hagerman RJ, Beckett LA, Hagerman PJ. Size bias of fragile X premutation alleles in late-onset movement disorders. J Med Genet 2006;43:804-9. Crossref

6. Uzielli ML, Guarducci S, Lapi E, et al. Premature ovarian failure (POF) and fragile X premutation females: from POF to fragile X carrier identification, from fragile X carrier diagnosis to POF association data. Am J Med Genet 1999;84:300-3. Crossref

7. Nolin SL, Glicksman A, Ding X, et al. Fragile X analysis of 1112 prenatal samples from 1991 to 2010. Prenat Diagn 2011;31:925-31. Crossref

8. Nolin SL, Brown WT, Glicksman A, et al. Expansion of the fragile X CGG repeat in females with premutation or intermediate alleles. Am J Hum Genet 2003;72:454-64. Crossref

9. Fernandez-Carvajal I, Lopez Posadas B, Pan R, Raske C, Hagerman PJ, Tassone F. Expansion of an FMR1 grey-zone allele to a full mutation in two generations. J Mol Diagn 2009;11:306-10. Crossref

10. Hill MK, Archibald AD, Cohen J, Metcalfe SA. A systematic review of population screening for fragile X syndrome. Genet Med 2010;12:396-410. Crossref

11. Chiang SC, Lee YM, Wang TR, Hwu WL. Allele distribution at the FMR1 locus in the general Chinese population. Clin Genet 1999;55:352-5. Crossref

12. Huang KF, Chen WY, Tsai YC, et al. Original article pilot screening for fragile X carrier in pregnant women of southern Taiwan. J Chin Med Assoc 2003;66:204-9.

13. Tzeng CC, Tsai LP, Hwu WL, et al. Prevalence of the FMR1 mutation in Taiwan assessed by large-scale screening of newborn boys and analysis of DXS548-FRAXAC1 haplotype. Am J Med Genet A 2005;133A:37-43. Crossref

14. Kwok YK, Wong KM, Lo FM, et al. Validation of a robust PCR-based assay for quantifying fragile X CGG repeats. Clin Chim Acta 2016;456:137-43. Crossref

15. Huang W, Xia Q, Luo S, et al. Distribution of fragile X mental retardation 1 CGG repeat and flanking haplotypes in a large Chinese population. Mol Genet Genomic Med 2015;3:172-81. Crossref

16. Han SH, Heo YA, Yang YH, Kim YJ, Cho HI, Lee KR. Prenatal population screening for fragile X carrier and the prevalence of premutation carriers in Korea. J Genet Med 2012;9:73-7. Crossref

17. Musci TJ, Moyer K. Prenatal carrier testing for fragile X: counseling issues and challenges. Obstet Gynecol Clin North Am 2010;37:61-70. Crossref

18. Song FJ, Barton P, Sleightholme V, Yao GL, Fry-Smith A. Screening for fragile X syndrome: a literature review and modelling study. Health Technol Assess 2003;7:1-106. Crossref

19. The Hong Kong Family Planning Association. The report on the Survey of Family Planning Knowledge, Attitude and Practice in Hong Kong 2012. Available from: http://www.famplan.org.hk. Accessed 21 Apr 2016.

20. Chopra M, Duan T. Rare genetic disease in China: a call to improve clinical services. Orphanet J Rare Dis 2015;10:140. Crossref

21. Leung TY, Chan LW, Law LW, et al. First trimester combined screening for trisomy 21 in Hong Kong: outcome of the first 10,000 cases. J Matern Fetal Neonat Med 2009;22:300-4. Crossref

22. Sahota DS, Leung TY, Fung TY, Chan LW, Law LW, Lau TK. Medians and correction of biochemical and ultrasound markers in Chinese undergoing first-trimester screening for trisomy 21. Ultrasound Obstet Gynecol 2009;33:387-93. Crossref

23. Leung TY, Chan LW, Leung TN, et al. First-trimester combined screening for trisomy 21 in a predominantly Chinese population. Ultrasound Obstet Gynecol 2007;29:14-7. Crossref

24. Sahota DS, Leung WC, To WK, Chan WP, Lau TK, Leung TY. Quality assurance of nuchal translucency for prenatal fetal Down syndrome screening. J Matern Fetal Neonatal Med 2012;25:1039-43. Crossref

25. Skinner D, Sparkman KL, Bailey DB Jr. Screening for fragile X syndrome: parent attitudes and perspectives. Genet Med 2003;5:378-84. Crossref

26. Acharya K, Ross LF. Fragile X screening: attitudes of genetic health professionals. Am J Med Genet A 2009;149:626-32. Crossref

27. Jacquemont S, Hagerman RJ, Hagerman PJ, Leehey MA. Fragile-X syndrome and fragile X–associated tremor/ataxia syndrome: two faces of FMR1. Lancet Neurol 2007;6:45-55. Crossref

28. Antenatal screening for fragile X syndrome: external review against programme appraisal criteria for the UK National Screening Committee (UK NSC). UK National Screening Committee; Oct 2014.

29. ACOG Committee Opinion No. 469: Carrier screening for fragile X syndrome. The American College of Obstetricians and Gynecologists Committee; Oct 2010.

Gastric cancer is the second most common cause of cancer-related mortality worldwide, with 988 000 new cases and 736 000 deaths per year.1 Surgery is the main treatment for operable gastric cancer but recurrence rates are high and about 40% to 80% of patients develop relapsed disease after surgery. The use of adjuvant chemotherapy has been shown to improve patient outcome.2 3 4 5 After curative resection, common adjuvant chemotherapy regimens that have been recently adopted in many parts of Asia include oral administration of S-1 (tegafur, gimeracil, and oteracil potassium) based on the Adjuvant Chemotherapy Trial of S-1 for Gastric Cancer (ACTS-GC) study conducted in Japan,4 as well as oxaliplatin-capecitabine combination chemotherapy based on the Capecitabine and Oxaliplatin Adjuvant Study in Stomach Cancer study.5 These studies have shown that adjuvant S-1 for 1 year or oxaliplatin-capecitabine combination chemotherapy for 6 months following curative gastrectomy with D2 lymph node dissection increases both overall survival (OS) and relapse-free survival in pathological stage II or III gastric cancer.4 5

S-1 is an oral anticancer agent comprising tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP), and oteracil potassium (Oxo) at a molar ratio of 1:0.4:1.6 Tegafur is a prodrug of 5-fluorouracil (5-FU); CDHP is a potent reversible inhibitor of 5-FU degradation; and Oxo is an inhibitor of the enzyme orotate phosphoribosyltransferase (OPRT) that catalyses the phosphorylation of 5-FU.6 Pharmacokinetic analyses have confirmed that S-1 has potent anti-tumour activity, and oral S-1 administration results in a similar serum concentration of 5-FU to intravenous 5-FU whilst sparing patients the need for continuous intravenous infusion of 5-FU and consequent toxicity.7 Nonetheless early studies have also shown that toxicity profiles may differ between Asian and non-Asian patients. In earlier studies in Japanese patients, the dose-limiting toxicity was bone marrow suppression that occurred prior to gastrointestinal adverse events. In contrast, studies in non-Asian patients revealed that diarrhoea associated with abdominal discomfort and cramping was the principal dose-limiting toxicity and bone marrow suppression was not.8 This might be due to the varied activity of OPRT between different populations. In fact, OPRT activates 5-FU in the bowel mucosa; patients with higher OPRT activity might be expected to experience a higher incidence of gastrointestinal adverse effects prior to bone marrow toxicity.9

In the ACTS-GC study, the adverse events of adjuvant S-1 were reported to be generally mild, with 65.8% of patients being able to complete the planned 1 year of therapy.4 While it has been known that patients in the West have a different toxicity profile to their Japanese counterparts,10 there are limited data on tolerability of S-1 among Chinese patients. In this multicentre retrospective study, we assessed the toxicity and tolerability profiles of Hong Kong Chinese patients with gastric cancer who had received adjuvant S-1 chemotherapy.

This was a retrospective study carrying out between June 2013 and February 2016, and involved six local centres in Hong Kong: Pamela Youde Nethersole Eastern Hospital, Princess Margaret Hospital, Prince of Wales Hospital, Tuen Mun Hospital, Queen Mary Hospital, and United Christian Hospital. This study has been approved by the institutional ethics committee of each participating centre with patient consent waived. Patients with stage II-IIIC gastric adenocarcinoma according to American Joint Committee on Cancer,11 who had completed curative surgical treatment and who had undergone S-1 adjuvant chemotherapy, were included. Patients with stage IV disease and who had had prior therapy with S-1 in the neoadjuvant setting were excluded.

Adjuvant S-1 was started at least 3 weeks after curative surgery. The intended dose of S-1 was based on that published in the ACTS-GC trial,4 and was 40 mg/m² twice daily for 4 weeks followed by 2 weeks of rest for each cycle. Specifically, during the treatment weeks, patients with body surface area (BSA) of <1.25 m² received 80 mg daily; those with BSA of 1.25 m² to <1.5 m² received 100 mg daily; and those with BSA of ≥1.5 m² received 120 mg daily. As clinically indicated, dose reductions were considered one dose level at a time; in general, one dose level reduction refers to reducing the prior daily dose by 20 mg, eg from 120 mg to 100 mg daily. As renal impairment has been associated with increased incidence of myelosuppression, dose reduction by one dose level was made in patients who had a creatinine clearance of 40-49 mL/min. A maximum of eight 6-weekly cycles were administered. The dose of S-1 was reduced in patients with significant toxicities, as assessed by the respective clinician-in-charge. Complete and differential blood count and serum chemistry were performed before each 6-week cycle. All patients had mid-cycle follow-up with complete and differential blood counts and serum chemistry in the first cycle.

Patient charts were reviewed by investigators at each centre for background information. S-1 chemotherapy records, as well as biochemical and haematological profiles, were extracted. Adverse events were graded according to the National Cancer Institute’s Common Terminology Criteria for Adverse Events (version 3.0).12 Adverse events were documented during chemotherapy and for 28 days after the last dose of S-1. Dose interruption was defined as a need for either any dose delay and/or dose reduction.

Clinical characteristics are summarised as number of patients and percentage (%) for categorical variables, and medians with ranges for continuous variables. The frequency of adverse events was tabulated. Factors independently associated with adverse events, dose interruptions, or earlier withdrawal of S-1 were identified using the Pearson’s Chi squared (χ²) test or the Fisher’s exact test if the expected number in any cell was less than five for categorical data or any cell with an expected count of less than one for categorical data, and t test or Wilcoxon rank-sum test for continuous data. A two-sided P value of <0.05 was considered significant. All statistical analyses were performed with SAS, version 9.3 (SAS Institute Inc, Cory [NC], US).

Disease-free survival (DFS) was calculated as the period from the date of surgery to the date of recurrence or death from any cause; OS was calculated as the period from the date of surgery to the date of death from any cause. Both DFS and OS were estimated using the Kaplan-Meier method.

Thirty patients met the eligibility criteria in the six centres during the study period and were enrolled in this study. Their baseline demographic and clinical characteristics are shown in Table 1.

There were 18 males and 12 females with a median age of 65.6 years. Of the patients, 27 (90%) had ECOG (Eastern Cooperative Oncology Group) performance status of 0 to 1. Total gastrectomy was performed in 11 (36.7%) patients and partial gastrectomy in 19 (63.3%). D2 dissection was performed in 26 (86.7%) patients and two had D1 dissection; the details of two other patients were unknown. The median number of lymph nodes resected was 31. Cancer stage II disease was present in 19 (63.3%) patients and stage III in 11 (36.7%).

Of the 30 patients, two (6.7%), two (6.7%), one (3.3%), two (6.7%), one (3.3%), three (10%), and 19 (63.3%) completed one, two, three, four, five, six, and eight cycles of S-1 adjuvant chemotherapy, respectively. At the time of data cut-off on 29 February 2016, one patient was still on S-1, having completed six cycles of treatment. The reasons for treatment withdrawal included toxicities (n=5, 16.7%), patient refusal (3, 10%), recurrence (2, 6.7%), and worsening of pre-existing Parkinson’s disease (1, 3.3%).

The median follow-up period was 25.3 months (range, 16.3-29.2 months). Three patients died and two experienced recurrence (lung and peritoneum). The 3-year DFS and OS rates were 80.2% and 85.9%, respectively (Fig).

Table 2 presents the haematological and non-haematological adverse events experienced during treatment. Grade 3-4 haematological adverse events included neutropaenia (n=3, 10%), leukopaenia (1, 3.3%), and anaemia (2, 6.7%). Grade 3-4 non-haematological adverse events included non-neutropaenic septic episode (16.7%), diarrhoea (6.7%), hyperbilirubinaemia (6.7%), syncope (6.7%), reduced left ventricular ejection function (3.3%), gouty attack (3.3%), hypokalaemia (3.3%), subacute intestinal obstruction (3.3%), and urticaria (3.3%).

Of note, 10 patients developed a septic episode; apart from one patient with grade 3 neutropaenic fever, the others were non-neutropaenic. Of the latter, four had grade 3 toxicity, four had grade 2, and one had grade 1 toxicity; in one patient with grade 2 toxicity, the infection was due to pulmonary tuberculosis. This latter patient had a history of ischaemic heart disease and he also developed grade 3 reduced left ventricular ejection function whilst on S-1, as noted above.

Two out of 30 patients were found to be positive for hepatitis B surface antigen. Of these two, one was prescribed prophylactic antiviral therapy and liver function remained normal apart from one isolated episode of grade 2 hyperbilirubinaemia that resolved spontaneously without other hepatic dysfunction; the other patient did not receive prophylactic antiviral therapy but his liver function remained normal throughout S-1 therapy.

There were no treatment-related deaths.

Of the 30 patients, 17 (56.7%) were commenced on a lower-than-intended dose of S-1. The reason for reducing the first dose was: impaired renal function (n=6; with creatinine clearance ranging from 41-48 mL/min), concern of toxicity (6), aged over 70 years (4), and borderline performance status (1); four of these patients had further dose reduction in subsequent cycles. Of the other 13 patients who had the full S-1 dose in cycle 1, five had a dose reduction from cycle 2 onwards.

Dose delays occurred in 12 (40%) patients; these were due to delayed bone marrow recovery (n=3), hypokalaemia (2, including 1 who also had delayed bone marrow recovery), diarrhoea (2), sepsis (2), hypoglycaemia (1), impaired renal function (1), reduced weight (1), and abdominal pain (1).

Potential risk factors for adverse events were assessed (Table 3). Univariate analysis showed that total gastrectomy was significantly associated with haematological adverse events; 90.9% of patients who had total gastrectomy in contrast to 52.6% of the patients who had partial gastrectomy experienced grade 2-4 adverse events (P=0.034). On univariate analysis, nodal status was significantly associated with non-haematological adverse events; 76.2% of patients who experienced grade 2-4 adverse events had nodal disease, while only 33% of those who had grade 0-1 adverse events had nodal disease (P=0.031).

Potential risk factors for earlier withdrawal of S-1 and dose interruptions (dose reductions and/or dose delays) were assessed (Table 4). For earlier S-1 withdrawal, patients who had a history of regular alcohol intake were significantly more likely to have earlier treatment withdrawal than non-drinkers (80% vs 28%; P=0.044), while ever-smokers also had a tendency, though insignificant, for earlier withdrawal than never-smokers (67% vs 29%; P=0.095). For dose interruptions, univariate analysis showed lower body weight (P=0.007) and lower BSA (P=0.017) were significant associated factors, while lower body mass index (BMI) also had an increased tendency, though insignificant, for dose interruptions (P=0.055). The median body weight, BMI, and BSA of those patients who had dose interruptions were 54.5 kg, 21.4 kg/m², and 1.54 m², respectively; the corresponding data for those who did not require dose interruptions were 64.0 kg, 24.8 kg/m², and 1.67 m², respectively.

Our study results indicate that adjuvant S-1 chemotherapy is feasible for our local patients after curative resection of gastric cancer. With increased awareness of the associated toxicity, S-1 can be offered safely as standard adjuvant therapy. The toxicities experienced by the studied patients were in line with previous findings in Asian patients.4 12 13 Grade 3-4 haematological adverse events included thrombocytopaenia and anaemia. Grade 3-4 non-haematological adverse events that occurred in 5% or more of the patients included non-neutropaenic septic episode, diarrhoea, hyperbilirubinaemia, and syncope.

Previous studies have investigated factors associated with adverse events during S-1 therapy. In a Korean study of 305 patients given adjuvant S-1 therapy,13 total gastrectomy was reported to be an independent risk factor for grade 3-4 haematological toxicities and age >65 years was an independent risk factor for grade 3 non-haematological toxicities. Independent risk factors for withdrawal and dose reductions included age >65 years and male gender. Total gastrectomy has also been reported to be associated with a significantly greater risk of serious adverse events in another study of Taiwanese gastric cancer patients receiving adjuvant S-1.14

The reason for the higher incidence of serious adverse events in patients who underwent total gastrectomy whilst receiving S-1 treatment is unknown. In an earlier study, a higher incidence of adverse reactions was observed among patients who received S-1 as adjuvant treatment after gastrectomy, compared with those who had unresectable or recurrent gastric cancer. The investigators suggested the limitation in food intake soon after extensive surgery as a possible cause of exacerbation of adverse reactions such as anorexia and nausea, and proposed that a delay in the start of drug administration after gastrectomy may prevent such adverse events.15 In another study, Taiwanese patients received palliative S-1 for advanced gastric cancer at a median initial dose of 37.0 mg/m². Twelve patients had single-dosing pharmacokinetic study on day 1, and seven took part in a multiple-dosing pharmacokinetic study on day 28. The results indicated that the steady-state pharmacokinetics of 5-FU, CDHP and Oxo could be predicted from single-dose pharmacokinetic study. Six patients who underwent gastrectomy had a similar pharmacokinetic profile to another six patients who did not undergo gastrectomy.16 Nonetheless, definitive data regarding the pharmacokinetic profile of S-1 components in patients who underwent different degrees of gastrectomy are lacking.

Other factors that have been reported to be associated with treatment-related adverse events include low body mass and impaired renal function.16 These were supported by the present study in which lower body weight, BMI, and BSA were associated with an increased likelihood of dose interruptions. Earlier reports have shown that impaired renal function will reduce CDHP clearance and result in a prolonged high concentration of 5-FU in plasma, and thereby lead to more severe myelosuppression.8 17 Although impaired renal function was not identified as a risk factor for adverse events in this study, it has to be noted that all patients who had subnormal creatinine clearance were offered S-1 at lower doses at treatment initiation; this could have prevented the occurrence of severe adverse events.

The present study was limited by its retrospective nature and the limited number of patients accrued. Although there is a lack of information about patient co-morbidities, the current data suggest that patients who had a history of regular alcohol intake had an increased likelihood of earlier treatment withdrawal. The survival data are immature due to short follow-up. The findings, however, lend support to a published report on the acceptable toxicity profile and tolerability of S-1 as adjuvant therapy after curative gastric surgery for gastric cancer.4 13 14 Potential risk factors for severe adverse events are suggested. Due to the small sample size and retrospective nature of this study, a prospective study with a larger patient population is needed to confirm these findings. An awareness of treatment-related adverse events as well as potential associated factors may aid clinicians in managing patients in whom S-1 therapy is planned, and thereby improve treatment compliance and clinical outcome.

Adjuvant S-1 therapy has a tolerable toxicity profile among local patients who have undergone curative resection for gastric cancer. For gastric cancer patients in whom adjuvant S-1 therapy is planned, those with identifiable risk factors should be closely monitored for adverse events during treatment. This may enable earlier intervention with supportive therapy and optimise treatment outcome.

The authors gratefully acknowledge Mr Edward Choi for his valuable statistical advice. We thank Drs Chi-ching Law, Hoi-leung Leung, and Chung-kong Kwan of the Department of Clinical Oncology, United Christian Hospital for their support in this study.

This study has been supported by an educational grant from Taiho Pharma Singapore Pte. Ltd. W Yeo has received honorarium for advisory role for Eli Lilly, Novartis, Pfizer, and Bristol Myers Squibb and has received research grant from Novartis over the past 12 months. KO Lam has been an advisor for Amgen, Eli Lilly, Roche, Sanofi-Aventis, and has received honorarium from Amgen, Bayer, Eli Lilly, Merck, Sanofi-Aventis, Taiho and research grant from Bayer, Roche, and Taiho. Authors not named here have disclosed no conflicts of interest.

1. Ferlay J, Shin HR, Bray F, Forman D, Mathers C, Parkin DM. GLOBOCAN 2008: Cancer incidence and mortality worldwide: IARC CancerBase No. 10. Lyon, France: International Agency for Research on Cancer; 2010. Available from: http://globocan.iarc.fr. Accessed 12 Oct 2011.

2. Gallo A, Cha C. Updates on esophageal and gastric cancers. World J Gastroenterol 2006;12:3237-42. Crossref

3. GASTRIC (Global Advanced/Adjuvant Stomach Tumor Research International Collaboration) Group, Paoletti X, Oba K, et al. Benefit of adjuvant chemotherapy for resectable gastric cancer: a meta-analysis. JAMA 2010;303:1729-37. Crossref

4. Sakuramoto S, Sasako M, Yamaguchi T, et al. Adjuvant chemotherapy for gastric cancer with S-1, an oral fluoropyrimidine. N Engl J Med 2007;357:1810-20. Crossref

5. Bang YJ, Kim YW, Yang HK, et al. Adjuvant capecitabine and oxaliplatin for gastric cancer after D2 gastrectomy (CLASSIC): a phase 3 open-label, randomised controlled trial. Lancet 2012;379:315-21. Crossref

6. Shirasaka T, Shimamato Y, Ohshimo H, et al. Development of a novel form of an oral 5-fluorouracil derivative (S-1) directed to the potentiation of the tumor selective cytotoxicity of 5-fluorouracil by two biochemical modulators. Anticancer Drugs 1996;7:548-57. Crossref

7. Kubota T. The role of S-1 in the treatment of gastric cancer. Br J Cancer 2008;98:1301-4. Crossref

8. Hirata K, Horikoshi N, Aiba K, et al. Pharmacokinetic study of S-1, a novel oral fluorouracil antitumor drug. Clin Cancer Res 1999;5:2000-5.

9. Chu QS, Hammond LA, Schwartz G, et al. Phase I and pharmacokinetic study of the oral fluoropyrimidine S-1 on a once-daily-for-28-day schedule in patients with advanced malignancies. Clin Cancer Res 2004;10:4913-21. Crossref

10. Ajani JA, Faust J, Ikeda K, et al. Phase I pharmacokinetic study of S-1 plus cisplatin in patients with advanced gastric carcinoma. J Clin Oncol 2005;23:6957-65. Crossref

11. Edge SB, Byrd DR, Compton CC, Fritz AG, Greene FL, Trotti A. American Joint Committee on Cancer. Cancer Staging Manual. 7th ed. Chicago: Springer; 2010.

12. Trotti A, Colevas AD, Setser A, et al. CTCAE v3.0: development of a comprehensive grading system for the adverse effects of cancer treatment. Semin Radiat Oncol 2003;13:176-81. Crossref

13. Jeong JH, Ryu MH, Ryoo BY, et al. Safety and feasibility of adjuvant chemotherapy with S-1 for Korean patients with curatively resected advanced gastric cancer. Cancer Chemother Pharmacol 2012;70:523-9. Crossref

14. Chou WC, Chang CL, Liu KH, et al. Total gastrectomy increases the incidence of grade III and IV toxicities in patients with gastric cancer receiving adjuvant TS-1 treatment. World J Surg Oncol 2013;11:287. Crossref

15. Kinoshita T, Nashimoto A, Yamamura Y, et al. Feasibility study of adjuvant chemotherapy with S-1 (TS-1; tegafur, gimeracil, oteracil potassium) for gastric cancer. Gastric Cancer 2004;7:104-9. Crossref

16. Chen JS, Chao Y, Hsieh RK, et al. A phase II and pharmacokinetic study of first line S-1 for advanced gastric cancer in Taiwan. Cancer Chemother Pharmacol 2011;67:1281-9. Crossref

17. Koizumi W, Kurihara M, Nakano S, Hasegawa K. Phase II study of S-1, a novel oral derivative of 5-fluorouracil, in advanced gastric cancer. For the S-1 Cooperative Gastric Cancer Study Group. Oncology 2000;58:191-7. Crossref

Retinopathy of prematurity (ROP) is a retinal vascular disease that affects premature infants in whom the retinal vasculature is not fully developed at the time of birth. The hyperoxic environment after birth—inclusive of room air—compared with the relative hypoxic intra-uterine environment suppresses the growth of retinal vessels (phase 1). Subsequently, growth of the retina increases metabolic demand and, in the background of incomplete retinal vascularisation, results in retinal hypoxia and ROP development (phase 2).1 2 3 Retinopathy of prematurity is characterised by the presence of abnormal retinal fibrovascular proliferation. Severe disease will progress to total retinal detachment and blindness if there is no intervention during the critical treatment period. Such retinopathy is one of the leading causes of visual impairment in children.4 5 6

The risk factors for ROP include low gestational age (GA), low birth weight (BW), presence of co-morbidities (eg patent ductus arteriosus [PDA], necrotising enterocolitis (NEC), intraventricular haemorrhage [IVH]), and a high level of supplemental oxygen.7 8 9 Those born at extreme prematurity and with extremely low birth weight (ELBW) are at high risk of severe ROP development. The British Guidelines published by the Royal College of Paediatrics and Child Health in 2008 recommended screening for ROP in premature infants with GA of <32 weeks or BW of <1501 g.10 The American Guidelines published by the American Academy of Pediatrics in 2013 recommended screening for ROP if GA was ≤30 weeks or BW ≤1500 g. Selected infants with BW of 1500 to 2000 g or GA of >30 weeks with an unstable clinical course should also be screened if they were assessed by the attending neonatologist to be at high risk of ROP.11 Since neonatal intensive care units and standards of health care have improved significantly in the past decade, more extreme preterm infants are surviving and a higher risk of ROP development is to be expected.12 13

The revised International Classification of Retinopathy of Prematurity was published in 2005.14 In this revised version, ROP was classified into five stages depending on the severity of retinal fibrovascular proliferation and into three zones depending on the location of vascularisation.14 Plus disease is characterised by the presence of severe retinal venous dilatation and arteriolar tortuosity, iris vascular engorgement, poor pupillary dilatation, and vitreous haze.14 Presence of plus disease indicates high disease activity.14 Aggressive posterior ROP is an uncommon, severe form of ROP characterised by posterior vascularisation, prominent plus disease, and rapid progression.14 Timely treatment is required for severe ROP to prevent retinal detachment and vision loss. Current guidelines suggest treatment if the ROP is type 1 pre-threshold defined by the Early Treatment for Retinopathy of Prematurity (ETROP) study,15 that is: (i) zone I, any stage of ROP, with plus disease; (ii) zone I, stage 3 ROP, with or without plus disease; or (iii) zone II, stage 2 or 3 ROP, with plus disease.10 11

The traditional mainstay of treatment is laser photocoagulation to ablate all avascular areas and reduce the ischaemic stress to allow the retinal fibrovascular proliferation to regress.10 11 Intravitreal injection of anti–vascular endothelial growth factor (anti-VEGF) agent has recently been advocated if ROP is in zone I, stage 3 with plus disease or aggressive posterior ROP.16 Operation with vitrectomy or scleral buckle surgery is required if retinal detachment has occurred but the results are often unsatisfactory.17 18 Proper screening and timely treatment are thus important measures to prevent retinal detachment and vision loss.

The prevalence of ROP and severe ROP that requires treatment vary among different countries. The reported prevalence of ROP ranged from 12.6% to 44.5%13 19 20 21 22 23 and that of severe ROP requiring treatment ranged from 1.5% to 11.7% in other countries.13 19 20 21 22 23 In Hong Kong, studies that report the prevalence and severity of ROP are scarce.24 25 The aim of this study was to evaluate the ROP prevalence, screening, and treatment outcome in a tertiary hospital in Hong Kong.

This was a retrospective cross-sectional study with internal comparison in which the medical records of eligible subjects were reviewed. All premature infants who were born at Queen Mary Hospital and had ROP screening performed between 1 January 2013 and 31 December 2013 were included. In this hospital, all infants are screened if the British screening criteria are met—GA of <32 weeks or BW of <1501 g. Those who died before ROP screening could be performed were excluded from this study. This study was done in accordance with the principles outlined in the Declaration of Helsinki.

All ROP screening was performed by two ophthalmologists who had experience in screening and treating ROP. All examinations were performed with binocular indirect ophthalmoscopy following pupil dilatation by topical mydriatic medication. The severity of ROP was graded according to the revised International Classification of Retinopathy of Prematurity.14 The screening protocol followed the British Guidelines published in 200810:

Data recorded included GA, BW, presence of co-morbidities, most severe ROP stage, any treatment given, and the treatment outcome. If the ROP stage was asymmetrical between the two eyes in an individual infant, the more severe ROP stage was measured.

Primary outcome measures included the prevalence of ROP of any stage and severe ROP that required treatment. Secondary outcome measures included association between risk factors of interest and risk of ROP development, and treatment outcome. The risk factors of interest studied included low GA, low BW, presence of respiratory distress syndrome (RDS), PDA, sepsis, NEC, IVH and the need for blood transfusion.

The Statistical Package for the Social Sciences (Windows version 23.0; SPSS Inc, Chicago [IL], US) was used to perform the statistical analysis. All continuous demographic data are expressed as mean ± standard deviation and categorical data are expressed as number (%). Further, GA and PMA are represented as number of weeks and the remaining days not completing a week written in superscript, eg 32 weeks and 5 days represented by 32⁺⁵ weeks. Chi squared test was used to evaluate the difference among subgroups for ROP development. Fisher’s exact test was used when the expected frequency of a cell in a table was <5. Risk factors that might predict ROP development were evaluated in univariate logistic regression analyses to calculate the odds ratio (OR) and 95% confidence interval. If there was more than one factor associated with a P value of <0.05 in univariate level, the risk factors would be entered into a multivariate logistic regression analysis with backward stepwise method. P<0.05 was considered to be statistically significant. All tests were two-sided.

A total of 92 infants met the British screening criteria during the study period of whom three died before ROP screening could be performed and were excluded from this study. Among the 89 infants screened, 52.8% were male. There were 49 (55.1%) singletons, 37 (41.6%) twins, and three (3.4%) triplets. The mean GA was 30⁺² weeks ± 16.5 days (range, 24⁺¹ weeks to 35⁺⁵ weeks; median, 30⁺⁴ weeks). The mean BW was 1285 g ± 328 g (range, 580 g to 2030 g; median, 1340 g). The distribution of infants in relation to GA and BW is shown in Table 1.

Of the 89 infants screened, 15 (16.9%) developed ROP at a mean time of 34⁺¹ weeks ± 13.0 days (range, 31⁺⁵ weeks to 38⁺⁴ weeks; median, 33⁺⁴ weeks), and three (3.4%) required treatment at a mean time of 40⁺² weeks ± 9.6 days (range, 39⁺² weeks to 41⁺⁶ weeks; median, 39⁺⁵ weeks). Nine (10.1%) infants developed stage 1 ROP, three (3.4%) developed stage 2 ROP, three (3.4%) developed stage 3 ROP, and none developed stage 4 or 5 ROP (Table 2).

Among the 15 infants who developed ROP, their mean GA was 27⁺¹ weeks ± 14.4 days (range, 24⁺¹ weeks to 30⁺² weeks; median, 27⁺⁵ weeks) and mean BW was 846 g ± 276 g (range, 580 g to 1530 g; median, 790 g).

In subgroup analysis, among the 17 ELBW infants of <1000 g, 12 (70.6%) developed ROP and three (17.6%) required treatment. Among the 12 extremely preterm infants with GA of <28 weeks, eight (66.7%) developed ROP and three (25.0%) required treatment (Table 2).

When the 2013 American screening criteria were applied retrospectively, 78 (87.6%) infants met the criteria. In the 11 (12.4%) infants whose GA and BW exceeded the 2013 American screening criteria, none of them developed any ROP.

In univariate logistic regression analysis, factors associated with risk of ROP development included low GA (OR=1.129 for each day decrease; P<0.001), low BW (OR=1.007 for each g decrease; P<0.001), RDS (OR=4.952; P=0.044), PDA (OR=12.904; P<0.001), sepsis (OR=4.787; P=0.013), and need for blood transfusion (OR=11.786; P<0.001) [Table 3]. In multivariate logistic regression analysis, factors associated with risk of ROP development included low BW (OR=1.006 for each g decrease; P<0.001) and PDA (OR=5.749; P=0.035) [Table 3].

Three infants developed severe ROP that required treatment (Table 4). Their mean GA was 25⁺¹ weeks ± 7.5 days (range, 24⁺¹ weeks to 26⁺² weeks; median, 25⁺¹ weeks) and mean BW was 708 g ± 79 g (range, 660 g to 800 g; median, 665 g). All received indirect diode laser photocoagulation treatment and all regressed after one laser treatment. No supplementary laser, intravitreal injection of anti-VEGF agent, or surgery was necessary.

This retrospective study identified the prevalence of ROP and severe ROP requiring treatment among premature infants in a tertiary hospital in Hong Kong. We observed a prevalence of ROP of 16.9% and that of severe ROP requiring treatment was 3.4%. Our prevalence was comparable to or less than that reported in most other countries. The reported prevalences of ROP were 29.2% in Singapore,19 37.8% in Southern Taiwan,20 21.6% in Southern India,21 12.6% in England,13 21.9% in Netherlands,22 and 44.5% in Brazil.23 The reported prevalences of severe ROP requiring treatment were 4.8% to 5.0% in Singapore,19 11.7% in Southern Taiwan,20 6.7% in Southern India,21 1.5% in England,13 and 1.8% in Brazil.23 In mainland China, the ROP screening included bigger infants with BW of up to 2000 g and GA of up to 34 weeks, and the reported prevalences of ROP and severe ROP requiring treatment were 17.8% and 6.8%, respectively.26 Since the risk of ROP among large infants is known to be small, the prevalence of ROP in mainland China could not be directly compared with our study.

Severe ROP is more prevalent in ELBW infants. Our study showed the prevalence of ROP was 70.6% and that of severe ROP requiring treatment was 17.6% in ELBW infants of <1000 g. This was comparable to another local study in Hong Kong in which 53.4% of ELBW infants developed ROP and 14.5% developed severe ROP requiring treatment.25 Our results are also comparable to those of other countries, where the prevalences of ROP and severe ROP requiring treatment in ELBW infants were 55.4% and 13.7% respectively in Singapore,19 70.7% and 29.3% respectively in Southern Taiwan,20 61.3% and 28.4% respectively in Northern Taiwan,27 and 55.9% and 19.4% respectively in Turkey.28 In this study, multivariate logistic regression analysis showed the risk of ROP development was significantly associated with low BW and presence of PDA. The association between PDA and risk of ROP development has been shown in previous studies.8 9 It has been postulated that persistent left-to-right shunt results in low systemic blood flow and retinal ischaemia, and thus is associated with higher risk of ROP development.8 29 In addition, use of indomethacin to close PDA might reduce retinal blood flow and contribute to ROP development.8 30

Dilated fundal examination in ROP screening is a stressful event for premature infants. It is important to screen only those who are at risk to avoid unnecessary examination and stress. In this study, 11 infants would not have been screened if the 2013 American screening criteria were used and none of them developed any ROP. This may suggest that the 2013 American Guidelines are more appropriate than the 2008 British Guidelines in reducing unnecessary examination.

In our study, all severe ROP (100%) regressed after one laser treatment without the need for repeat treatment. No infants developed stage 4 or above ROP. This reflects a good standard of neonatal care in Hong Kong. In Southern Taiwan, 16.9% progressed to stage 4 or 5 ROP requiring further intervention after initial treatment.20 In mainland China, 4.2% of stage 3 ROP and 28.6% of aggressive posterior ROP progressed to retinal detachment after initial treatment.26

Our study highlights the importance of proper screening and timely treatment to prevent retinal detachment and severe vision loss due to ROP. We recommend strict adherence to international screening guidelines, and all ROP screening should be performed by ophthalmologists with dilated fundal examination.10 Since ELBW infants have a high risk of ROP and need for treatment, early parent education and good communication with anticipation for treatment will be helpful. For premature infants transferred from other hospitals for non-ophthalmological conditions, attention should be paid to the ROP screening record and examinations should be performed if the screening criteria are met. Good communication between hospital units is crucial to ensure continuous care and that these infants do not miss ROP screening and thus the window of opportunity for treatment.

There were several limitations in this study. First, the sample size was small. Second, due to the retrospective design, this study was not able to evaluate other potential risk factors that might increase the risk of ROP development. The level of oxygen therapy was not evaluated because it could not be assessed accurately in view of frequent changing of arterial oxygen saturation level and percentage of oxygen administered. Last, this study reviewed only those who had received ROP screening or treatment, therefore we were not able to evaluate those who died before being screened.

Retinopathy of prematurity is an important health problem among premature infants in Hong Kong, especially those with ELBW. The results of our study suggest that the current screening service and treatment outcome are satisfactory. Strict adherence to international screening guidelines and vigilance in infants at risk are key to successful ROP management.

All authors have disclosed no conflicts of interest.

1. Hartnett ME, Penn JS. Mechanisms and management of retinopathy of prematurity. N Engl J Med 2012;367:2515-26. Crossref

2. Hartnett ME. Pathophysiology and mechanisms of severe retinopathy of prematurity. Ophthalmology 2015;122:200-10. Crossref

3. Hellström A, Smith LE, Dammann O. Retinopathy of prematurity. Lancet 2013;382:1445-57. Crossref

4. Kong L, Fry M, Al-Samarraie M, Gilbert C, Steinkuller PG. An update on progress and the changing epidemiology of causes of childhood blindness worldwide. J AAPOS 2012;16:501-7. Crossref

5. Furtado JM, Lansingh VC, Carter MJ, et al. Causes of blindness and visual impairment in Latin America. Surv Ophthalmol 2012;57:149-77. Crossref

6. Haddad MA, Sei M, Sampaio MW, Kara-José N. Causes of visual impairment in children: a study of 3,210 cases. J Pediatr Ophthalmol Strabismus 2007;44:232-40.

7. Sylvester CL. Retinopathy of prematurity. Semin Ophthalmol 2008;23:318-23. Crossref

8. Thomas K, Shah PS, Canning R, Harrison A, Lee SK, Dow KE. Retinopathy of prematurity: Risk factors and variability in Canadian neonatal intensive care units. J Neonatal Perinatal Med 2015;8:207-14. Crossref

9. Hadi AM, Hamdy IS. Correlation between risk factors during the neonatal period and appearance of retinopathy of prematurity in preterm infants in neonatal intensive care units in Alexandria, Egypt. Clin Ophthalmol 2013;7:831-7. Crossref

10. Wilkinson AR, Haines L, Head K, Fielder AR. UK retinopathy of prematurity guideline. Early Hum Dev 2008;84:71-4. Crossref

11. Fierson WM; American Academy of Pediatrics Section on Ophthalmology; American Academy of Ophthalmology; American Association for Pediatric Ophthalmology and Strabismus; American Association of Certified Orthoptists. Screening examination of premature infants for retinopathy of prematurity. Pediatrics 2013;131:189-95. Crossref

12. Chamney S, McGrory L, McCall E, et al. Treatment of retinopathy of prematurity in Northern Ireland, 2000-2011: a population-based study. J AAPOS 2015;19:223-7. Crossref

13. Painter SL, Wilkinson AR, Desai P, Goldacre MJ, Patel CK. Incidence and treatment of retinopathy of prematurity in England between 1990 and 2011: database study. Br J Ophthalmol 2015;99:807-11. Crossref

14. International Committee for the Classification of Retinopathy of Prematurity. The International Classification of Retinopathy of Prematurity revisited. Arch Ophthalmol 2005;123:991-9. Crossref

15. Good WV; Early Treatment for Retinopathy of Prematurity Cooperative Group. Final results of the Early Treatment for Retinopathy of Prematurity (ETROP) randomized trial. Trans Am Ophthalmol Soc 2004;102:233-50.

16. Mintz-Hittner HA, Kennedy KA, Chuang AZ; BEAT-ROP Cooperative Group. Efficacy of intravitreal bevacizumab for stage 3+ retinopathy of prematurity. N Engl J Med 2011;364:603-15. Crossref

17. Asano MK, Papakostas TD, Palma CV, Skondra D. Visual outcomes of surgery for stage 4 and 5 retinopathy of prematurity. Int Ophthalmol Clin 2014;54:225-37. Crossref

18. Yu YS, Kim SJ, Kim SY, Choung HK, Park GH, Heo JW. Lens-sparing vitrectomy for stage 4 and stage 5 retinopathy of prematurity. Korean J Ophthalmol 2006;20:113-7. Crossref

19. Shah VA, Yeo CL, Ling YL, Ho LY. Incidence, risk factors of retinopathy of prematurity among very low birth weight infants in Singapore. Ann Acad Med Singapore 2005;34:169-78.

20. Li ML, Hsu SM, Chang YS, et al. Retinopathy of prematurity in southern Taiwan: a 10-year tertiary medical center study. J Formos Med Assoc 2013;112:445-53. Crossref

21. Rao KA, Purkayastha J, Hazarika M, Chaitra R, Adith KM. Analysis of prenatal and postnatal risk factors of retinopathy of prematurity in a tertiary care hospital in South India. Indian J Ophthalmol 2013;61:640-4. Crossref

22. van Sorge AJ, Termote JU, Kerkhoff FT, et al. Nationwide inventory of risk factors for retinopathy of prematurity in the Netherlands. J Pediatr 2014;164:494-8.e1. Crossref

23. Gonçalves E, Násser LS, Martelli DR, et al. Incidence and risk factors for retinopathy of prematurity in a Brazilian reference service. Sao Paulo Med J 2014;132:85-91. Crossref

24. Yau GS, Lee JW, Tam VT, Liu CC, Wong IY. Risk factors for retinopathy of prematurity in extremely preterm Chinese infants. Medicine (Baltimore) 2014;93:e314. Crossref

25. Yau GS, Lee JW, Tam VT, Liu CC, Chu BC, Yuen CY. Incidence and risk factors for retinopathy of prematurity in extreme low birth weight Chinese infants. Int Ophthalmol 2015;35:365-73. Crossref

26. Xu Y, Zhou X, Zhang Q, et al. Screening for retinopathy of prematurity in China: a neonatal units–based prospective study. Invest Ophthalmol Vis Sci 2013;54:8229-36. Crossref

27. Yang CY, Lien R, Yang PH, et al. Analysis of incidence and risk factors of retinopathy of prematurity among very-low-birth-weight infants in North Taiwan. Pediatr Neonatol 2011;52:321-6. Crossref

28. Bas AY, Koc E, Dilmen U; ROP Neonatal Study Group. Incidence and severity of retinopathy of prematurity in Turkey. Br J Ophthalmol 2015;99:1311-4. Crossref

29. Saldeño YP, Favareto V, Mirpuri J. Prolonged persistent patent ductus arteriosus: potential perdurable anomalies in premature infants. J Perinatol 2012;32:953-8. Crossref

30. Jegatheesan P, Ianus V, Buchh B, et al. Increased indomethacin dosing for persistent patent ductus arteriosus in preterm infants: a multicenter, randomized, controlled trial. J Pediatr 2008;153:183-9. Crossref