Genomics of Hereditary Colorectal Cancer: Lessons Learnt from 25 Years of the Singapore Polyposis Registry

<p><b>INTRODUCTION</b>The Singapore Polyposis Registry (SPR) was established in 1989 in Singapore General Hospital (SGH). The aims were to provide a central registry service to facilitate identification, surveillance and management of families and individuals at high risk of colorectal cancer.</p><p><b>MATERIALS AND METHODS</b>This is a review of published literature in the department.</p><p><b>RESULTS</b>The registry currently has 253 families with several genetic conditions-93 familial adenomatous polyposis (FAP) families, 138 Amsterdam-criteria positive presumed Lynch syndrome (LS) families, 12 families with Peutz Jeghers syndrome, 2 families with Cowden's syndrome, and 8 families with hereditary mixed polyposis syndrome (HMPS). There are also 169 families with a strong family history of colorectal cancer but no abnormal genes yet identified. In FAP, a diagnostic tool developed has allowed a 94% local APC germline detection rate in FAP families. Knowledge obtained studying the phenotype of FAP patients has allowed better choice of surgery between ileal pouch anal anastomosis (IPAA) against an ileal-rectal anastomosis (IRA). In LS, our review has noted a highly heterogenous mutational spectrum and novel variants made up 46.7% (28/60) of all variants identified in this cohort. This may suggest that our Southeast Asian ethnic groups have distinct mutational variants from Western populations. Pathogenic mutations were only confined to MLH1 and MSH2, and identified in 28.8% of families.</p><p><b>CONCLUSION</b>The impact of predictive gene testing for hereditary cancer risk in clinical practice has allowed evolution of care. Risk-reducing surgery and aggressive surveillance allows reduction in morbidity and mortality of patients. The SPR will continue to grow and improve outcomes in hereditary colorectal cancer patients and families.</p>

Peutz-Jeghers syndrome: data from the Singapore Polyposis Registry and a shifting paradigm in management

<p><b>INTRODUCTION</b>Peutz-Jeghers Syndrome (PJS) is an uncommon autosomal dominant hamartomatous polyposis syndrome. Morbidity arises from polyp-related complications and increased risks of malignancy. We report on PJS patients registered in the Singapore Polyposis Registry, identified principal causes of morbidity and appraised current management strategies. A followup protocol based on recent literature has been proposed.</p><p><b>MATERIALS AND METHODS</b>A search of a prospectively collected database in the Singapore Polyposis Registry was made. Only patients who fulfilled the diagnostic criteria of PJS were included. The clinical records were retrieved for review. Information on affected family members was obtained from the Registry's pedigree records.</p><p><b>RESULTS</b>Seven unrelated patients fulfilled the criteria of having PJS. Principal causes of morbidity include recurrent bouts of abdominal colic, episodes of intestinal obstruction, gastrointestinal bleeding and the need for repeated laparotomies. Six out of 7 patients had initial presentation with acute intestinal obstruction requiring emergency laparotomy. Management was mostly problem-oriented and marked inter-surgeon variation with regard to cancer screening and genetic counselling was observed.</p><p><b>CONCLUSION</b>Patients with PJS suffer gastrointestinal complications from polyposis and are at increased risks for developing cancers. A move towards surveillance and planned comprehensive care may reduce the morbidity of the condition. A protocol driven approach conducted in the setting of a Polyposis Registry is ideally suited to facilitate such care.</p>