Prospective and retrospective analysis of colonoscopy findings in patients with a history of colorectal carcinoma in first-degree relatives.

The frequency of colorectal neoplasia was assessed by colonoscopy in 48 patients with a history of colorectal cancer in a first-degree relative. Twelve of these patients were found to have polyps in the colon, including 1 who had invasive cancer. Patients with multiple first-degree relatives who have a history of colorectal cancer were found to be at increased risk, 56% having colonoscopic findings positive for polyps. Of the 12 patients with positive colonoscopic findings, 5 (42%) had multiple lesions. These findings are similar to those reported in recent pedigree studies and further support a genetic basis for common colorectal cancer. First-degree relatives of patients with colorectal cancer should be considered a high-risk group for colorectal neoplasia. Screening with colonoscopy is recommended.