Abstract
BACKGROUND: Hereditary Non-Polyposis Colorectal cancer is caused by Lynch Syndrome (LS; an autosomal dominant condition) or by Familial Colorectal Cancer Type-X (FCCTX; a condition of high family risk that fulfills Amsterdam criteria). The lifetime risk of developing colorectal cancer (CRC) in FCCTX family members is high and CRC occurs later than in LS. METHODS: To determine the impact of primary prevention colonoscopic screening in asymptomatic first-degree relatives of incident CRC cases in 20 families with FCCTX, we compared cancer incidence and survival in 79 males and 83 females, assumed to be at 50% risk of inheriting a genetic CRC susceptibility factor, who entered screening to an unscreened control group from the families, matched for age at entry into screening and for sex. RESULTS: In males, median age at entry into screening was 44.8 years, median follow-up 12.4 years, 12% developed CRC, and 46% died after 30 years of follow-up. Compared to the unscreened group, relative risk of CRC was 0.27 (95% confidence intervals (CI) 0.10-0.71). In screened females, comparable results were 44.5 years at entry, 11.2 years of follow-up, 7.1% developed CRC, and 7.2% died after 30 years of follow-up. The relative risk of CRC compared to the unscreened group was 0.19 (95% CI 0.07-0.48). CONCLUSION: Primary prevention screening colonoscopy in asymptomatic family members significantly decreased the risk of CRC in FCCTX.