OWE-25 Patients with multiple adenomas in bowel cancer screening program are not referred for genetic testing

IntroductionApproximately one in twenty cases of colorectal cancer (CRC) are associated with germline mutations that confer higher susceptibility to the disease. Guidelines recommend that patients with ten or more adenomas be referred for genetic testing1, with evidence that suggests >9% of these patients with 1–9 adenomas have a highly penetrant CRC predisposition syndrome2. The primary aim of this study was to quantify patients with ten or more adenomas in the West London (WL) and North Central London (NCL) Bowel Cancer Screening program (BCSP) centres. The secondary aim was to determine what proportion of these multiple adenoma patients were referred for genetic screening.MethodsA retrospective cross-sectional study was performed of patients who underwent colonoscopy following a positive faecal occult blood test (FOBt) as part of the WL and NCL BCSPs between May 2007 &amp June 2018. All polyps were examined histologically and only confirmed adenomas were included. Clinicopathological data including age and gender was recorded from BCSP patient records. Referrals to regional clinical genetics services were ascertained. Statistical analysis was performed in Graphpad Prism.Results11,337 patients underwent colonoscopy following positive FOBt and 5,650 (49.8%) had 1 or more adenomas. 107 patients (0.94%) had 10 or more adenomas. The proportion of patients with 10 or more adenomas was higher in NCL BCSP (1.1%) than in WL BCSP (0.7%) (p=0.02; χ2 test). 42 patients presented with 10 or more metachronous adenomas at the index colonoscopy or following an early follow up procedure; the remaining 65 patients undergoing excision of a total of 10 or more metachronous adenomas after subsequent surveillance colonoscopy. An accurate family history was not routinely collected in this population. Of the 107 patients with 10 or more adenomas, only 3 (2.8%) were referred to a clinical genetics service.ConclusionsIn two London BCSP centres, patients with ten or more metachronous adenomas are an uncommon finding. Despite guidelines advising genetic testing in this group, referral rates are low. A referral pathway and management strategies should be established to address this patient population.ReferencesHampel H, Bennett RL, Buchanan A, et al. A practice guideline from the American College of Medical Genetics and Genomics and the National Society of Genetic Counselors: referral indications for cancer predisposition assessment. Genet Med 2015;17:7–7.Grover S, Kastrinos F, Ste