Colonoscopic screening in first-degree relatives of patients with 'sporadic' colorectal cancer: a case-control study. The Association Nationale des Gastroentérologues des Hôpitaux and Registre Bourguignon des Cancers Digestifs (INSERM CRI 9505).

Background & Aims: A screening policy has not been well defined in first-degree relatives of patients with sporadic colorectal cancer. This study estimated the risk of colorectal adenoma in a cohort of individuals with only 1 affected first-degree relative.

Methods: A total of 476 first-degree relatives (age, 40-74 years) of 195 patients with sporadic colorectal cancer were offered a colonoscopy. Each examined relative was matched with 2 controls for age, sex, symptoms, and center. The prevalence of colorectal adenomas was compared using a multiple logistic regression analysis.

Results: In 185 relatives, odds ratios were 1.5 (95% confidence interval [CI], 1.0-2.4) for adenomas, 2.5 for large adenomas (95% CI, 1.1-5.4), 1.2 for small adenomas (95% CI, 0.7-1.9), and 2.6 (95% CI, 1.3-5.1) for high-risk adenomas (> or = 1 cm in size and/or with a villous component). The prevalence of high-risk adenomas in relatives was higher when the index patient was younger than 65 years, was male, and had distal rather than proximal cancer.

Conclusions: Subjects with only 1 affected first-degree relative are at increased risk for developing large adenomas.