Lack of effect of a high-fiber cereal supplement on the recurrence of colorectal adenomas

Background: The risks of colorectal cancer and adenoma, the precursor lesio n, are believed to be influenced by dietary factors. Epidemiologic evidence that cereal fiber protects against colorectal cancer is equivocal. We cond ucted a randomized trial to determine whether dietary supplementation with wheat-bran fiber reduces the rate of recurrence of colorectal adenomas. Methods: We randomly assigned 1429 men and women who were 40 to 80 years of age and who had had one or more histologically confirmed colorectal adenom as removed within three months before recruitment to a supervised program o f dietary supplementation with either high amounts (13.5 g per day) or low amounts (2 g per day) of wheat-bran fiber. The primary end point was the pr esence or absence of new adenomas at the time of follow-up colonoscopy. Sub jects and physicians, including colonoscopists, were unaware of the group a ssignments. Results: Of the 1303 subjects who completed the study, 719 had been randoml y assigned to the high-fiber group and 584 to the low-fiber group. The medi an times from randomization to the last follow-up colonoscopy were 34 month s in the high-fiber group and 36 months in the low-fiber group. By the time of the last follow-up colonoscopy, at least one adenoma had been identifie d in 338 subjects in the high-fiber group (47.0 percent) and in 299 subject s in the low-fiber group (51.2 percent). The multivariate adjusted odds rat io for recurrent adenoma in the high-fiber group, as compared with the low- fiber group, was 0.88 (95 percent confidence interval, 0.70 to 1.11; P=0.28 ), and the relative risk of recurrence according to the number of adenomas, in the high-fiber group as compared with the low-fiber group, was 0.99 (95 percent confidence interval, 0.71 to 1.36; P=0.93). Conclusions: As used in this study, a dietary supplement of wheat-bran fibe r does not protect against recurrent colorectal adenomas. (N Engl J Med 200 0;342:1156-62.) (C) 2000, Massachusetts Medical Society.