Impact of a Family History of Colorectal Cancer on the Prevalence of Advanced Neoplasia at Colonoscopy in 4,967 Asymptomatic Patients

A family history of colorectal cancer is considered an independent risk factor for advanced neoplasia at colonoscopy. The expected outcome for screening colonoscopy in patients with a family history is not well established in all populations. 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 neoplasia on screening colonoscopy. We evaluated 6,905 consecutive patients referred for colonoscopy between January 2005 and December 2006. Of the 4,967 who met the inclusion criteria, the mean age was 58.8 and consisted of 58.6% women. Overall 930 (18.7%) had neoplasia and 249 (5%) had advanced neoplasia, eight (0.16%) of which were cancer. The 4,967 patients were divided into 643 with and 4,324 without a family history of colorectal cancer. Of the 643 patients with a family history, 38 (5.9%) had advanced neoplasia, one of which was cancer. Of the 4,324 patients without a family history, 211 (4.9%) had advanced neoplasia including seven cancers. The relative risk for finding advanced neoplasia in patients with a single affected first degree relative was 1.21 (95% CI, 0.87-1.69; P = 0.31). A family history of one first-degree relative with colorectal cancer did not predict a significantly higher prevalence of advanced neoplasia at screening colonoscopy in this Southwestern cohort.