The effect of attending a flexible sigmoidoscopic screening program on theprevalence of colorectal adenomas at 13-year follow-up

OBJECTIVES: Understanding the epidemiology of colorectal adenomas is a prer equisite for designing follow-up programs after polypectomy. The aim of the study was to investigate the effect of polypectomy on the long-term preval ence of adenomas. METHODS: In 1983, a total of 799 men and women aged 50-59 yr were drawn fro m the general population register. Of these, 400 comprised a screening grou p and 399 a matched control group. The screenees were invited to undergo a once-only flexible sigmoidoscopy. Persons with polyps had a baseline colono scopy with follow-ups in 1985 and 1989. In 1996, both the screenees and the controls were invited to a colonoscopic examination. RESULTS: In 1996, a t otal of 451 (71%) individuals attended. Adenomas were found in 78 (37%) ind ividuals in the screening group and 103 (43%) in the control group, relativ e risk (95% confidence interval): 0.9 (0.7-1.1), p = 0.3, and high-risk ade nomas (severe dysplasia, adenomas greater than or equal to 10 mm, villous c omponents) were found in 16 (8%) and 32 (13%), respectively; relative risk (95% confidence interval): 0.6 (0.3-1.0), p = 0.07. CONCLUSIONS: There was no significant difference in adenoma prevalence betw een the group after the screening program and the controls after the usual care. There was a trend toward more high-risk adenomas in the control group . This suggests a very limited effect of one-time screening sigmoidoscopy w ith surveillance colonoscopy on the prevalence of adenomas, but a preventiv e effect on the development of high-risk adenomas consistent with the repor ted effect on cancer prevention. (C) 2001 by Am. Coll. of Gastroenterology.