Prevalence of colorectal adenomas in individuals with a family history of colorectal cancer based on initial colonoscopy: Implications for colonoscopic surveillance

Background: Increasing evidence suggests that inherited susceptihility is an important factor in the pathogenesis of colorectal adenomas and colorectal cancer; because of that, screening strategies that consider familial risk could increase their effectiveness. Aims : The aim of this study was to know the risk for colorectal adenomas, colorectal cancer and extracolonic cancers in first degree relatives of patients with colorectal adenomas. Methods and Patients : We evaluated patients referred to our institution for initial colonoscopy between June 1996 and July 1997 who did not have a family or personal history of familial polyposis, inflammatory bowel disease neither previous polypectomies or colorectal cancer (n= 379). Patients were divided in two groups: Group A) patients with complete colonoscopy with removal of one or more adenomas (n= 164) and. Group B) patients with complete colonoscopy without adenomas (n= 215). Mean age in group A and B was 62 and 61 respectively (p= NS).As well, no significant differences in sex between group A (MIF 40%/60%) and group B (MIF 52%/48%). They all were interviewed in order to determine if history of colorectal adenomas, colorectal cancer or extracolonic cancers had been documented in their first degree relatives . Result s:A mong first degree relatives of patients with adenomas (n= 1132). 12 ( J.I %) had personal history of colorectal adenomas. 19 (1.7%) of colorect al cancer and 16 ( 1.4%) antecedents of extracolonic cancer. In the group of first degree relatives of those without adenomas (n= 1478). 3 ( 0.2%) had personal history of colorectal adenomas, 16 ( J.I %) of colorec tal cancer and 17 ( 1.1 %) antecedents of extracolon ic cancer. Odds Ratio for colorectal adenomas, colorectal cancer and extracolonic cancers in the relatives of the patients with adenomas as compared with controls was 5 27 ( 95% CI: 1.38-23.53; p=0.009*), 1.72 (95 % CI: 0.79-3.76; p=0.19) and 1.23 (95% CI: 0.59-2.57; p= 0.67) respectively. Conclusions:First degree relatives of patients with newly diagnosed adenomas are at increased risk for developing colorectal adenomas. It supports a familial predisposition for these premalignant lesions and suggests that total colonoscopy screening could be indicated in these subjects.