Designing a Model to Implement a Cost-Effective High-Risk Cancer Strategy within the National BowelScreen Programme

Hereditary factors are thought to play a role in up to 35% of colorectal cancers (CRCs) with defined hereditary cancer syndromes accounting for 5-10% of cases. Lynch Syndrome (LS) is the most common cause of hereditary CRC. Other hereditary CRC syndromes include adenomatous and serrated polyposis syndromes which are characterised by multiple polyps and an increased risk of CRC. There are currently no national guidelines for the management of hereditary CRC in Ireland and management is largely determined by the local clinical site an individual attends. The aim of this study was to determine the prevalence of possible LS, adenomatous polyposis syndromes and serrated polyposis syndromes in a colorectal cancer screening cohort. In addition, we examined the current approaches to the management of hereditary CRC in Ireland and using this data have proposed a model to develop a national service for hereditary CRC. Universal testing of all CRCs for LS aims to increase detection. In our cohort 89% of CRCs were tested for LS and 7.6% were found to have MMR deficiency. After further testing 1.6% had an indication to be referred for genetic testing. Ultimately no individual proceeded to genetic testing so the true prevalence of LS in our cohort remains unknown. In terms of polyposis syndromes 0.8% of the study population met criteria to be considered for genetic testing based on BSG guidance for multiple colorectal adenomas and 0.3% met WHO criteria for SPS. Few individuals who met these criteria had been recognised previously. Through a survey of BowelScreen screening sites we have examined the current approach to managing hereditary CRC in Ireland and have identified key areas that could be targeted to improve management including testing all CRCs for LS, maintaining a database or registry for hereditary CRC and improving access to clinical genetic services. Using this data, we have proposed a national service for the management of hereditary CRC in Ireland which could be incorporated into BowelScreen, the national CRC screening programme, given its existing high-quality endoscopy, multidisciplinary teams and robust recall mechanisms. In addition, a cost-effective analysis has shown testing all BowelScreen detected CRCs for LS to be effective in terms of CRCs detected and deaths prevented.