Incidence of Advanced Adenomas of the Rectosigmoid Colon Three Years and Five Years After Negative Flexible Sigmoidoscopy in 4010 Patients

Flexible sigmoidoscopy is recommended for persons at average risk for colorectal cancer. A follow-up is advised in 3 to 5 years, although the outcomes are not well established. We designed a large, prospective study of an unselected population to measure the incidence of advanced adenomas at flexible sigmoidoscopy 3 and 5 years after an initial negative examination. Adenomas were considered advanced if they were villous, tubulovillous, high-grade dysplasia, adenocarcinoma, or ≥10 mm in size. We evaluated 8121 patients referred for flexible sigmoidoscopy and 4010 met the inclusion criteria. Group 1 had flexible sigmoidoscopy between 3 and 4 years and Group 2 between 5 and 6 years after a negative examination. Group 1 included 1300 patients with an incidence rate for advanced adenomas of 0.9% (12/1300) and Group 2 included 2710 patients with an incidence rate for advanced adenomas of 1.1% (30/2710). When the two group were subdivided by the presence or absence of a family history of a first-degree relative with sporadic colorectal cancer, the incidence rates for advanced adenomas between the populations were not different. Our data indicate incidence rates of 0.9 and 1.1% for advanced adenomas at flexible sigmoidoscopy 3 and 5 years, respectively, after a negative flexible sigmoidoscopy, with no impact from a family history.