Family History of Single First-Degree Relative with Colorectal Cancer Does Not Predict Increased Risk of Advanced Adenomas On Screening Colonoscopy in a Southwestern U.S. Population

Abstract

Background and Aims: A family history of colorectal cancer is considered a risk factor for finding advanced adenomas on colonoscopy. The expected outcome for screening colonoscopy in patients with a family history is not well established in all populations. Methods: We designed a large, prospective study of an unselected population in San Diego, California to assess the impact of a family history of colorectal cancer on the prevalence of advanced adenomas on screening colonoscopy. Asymptomatic patients between ages 40 to 89 referred for screening colonoscopy were included. Family history of colorectal cancer was defined as having at least one first-degree relative with colorectal cancer. Family history was obtained from review of medical records. Advanced adenoma was defined as having size ≥ 10 mm, villous features, dysplasia or carcinoma. Results: We evaluated 6,185 patients referred for colonoscopy between January 2005 and July 2006. 4,377 patients met the inclusion criteria. 833 (19%) had an adenoma and 225 (5.1%) had an advanced adenoma, 10 of which had carcinoma. The 4,377 patients were divided into 469 with and 3906 without a family history of colorectal cancer. Of the 469 patients with a family history, 31 (6.6%) had an advanced adenoma, none of which were carcinomas. Of the 3,906 without a family history, 194 (5.0%) had an advanced adenoma including 10 carcinomas (0.3%). The odds ratio for finding an advanced adenoma in patients with a family history was 1.35 (95%CI = 0.92-2.00; p = .18). If the affected relative was <60 at age of diagnosis the odds ratio was 1.52 (95%CI = 0.85-2.72). These differences were not statistically significant. An advanced adenoma was found in 26/428 (6.1%) of patients with a single affected first-degree relative (OR 1.22; 95%CI = 0.80-1.86; p = .41), 1/33 (3.0%) of patients with an affected first and second-degree relative (OR 0.58; 95%CI = 0.08-4.28; p = 1) and 4/18 (22.2%) of patients with two affected first-degree relatives (OR 5.42; 95%CI = 1.77-16.6; p = .02). When separated by gender, 118/1829 (6.5%) of men and 107/2548 (4.2%) of women had an advanced adenoma (OR 1.57; 95%CI = 1.20-2.06; p = .002). Conclusions: A family history of one first-degree relative with colorectal cancer did not predict a higher prevalence of advanced adenomas in asymptomatic patients at screening colonoscopy in this Southwestern cohort. Significant predictors of advanced adenomas were family history of two first-degree relatives with colorectal cancer and male gender. These data suggest the need to reassess the impact of a family history of a single first-degree relative with colorectal cancer on the prevalence of advanced adenomas in regional populations.