AIM:To investigate whether,under the influence of pol-ypectomy,the incidence of adenoma decreases with age.METHODS:Consecutive patients with colonic adenomas identified at index colonoscopy were retrospectively selected if they had undergone three or more complete colonoscopies,at least 24 mo apart.Patients who had any first-degree relative with colorectal cancer were excluded.Data regarding number of adenomas at each colonoscopy,their location,size and histological classification were recorded.The monthly incidence density of adenomas after the index examination was estimated for the study population,by using the person-years method.Baseline adenomas were excluded from incidence calculations but their characteristics were correlated with recurrence at follow-up,using the χ 2 test.RESULTS:One hundred and fifty-six patients were included(109 male,mean age at index colonoscopy 56.8 ± 10.3 years),with follow-up that ranged from 48 to 232 mo.No significant correlations were observed between the number,the presence of villous component,or the size of adenomas at index colonoscopy and the presence of adenomas at subsequent colonoscopies(P = 0.49,0.12 and 0.78,respectively).The incidence of colonic adenomas was observed to decay from 1.4% person-months at the beginning of the study to values close to 0%,at 12 years after index colonoscopy.CONCLUSION:Our results suggest the sporadic formation of adenomas occurs within a discrete period and that,when these adenomas are removed,all neoplasia-prone clones may be extinguished. AIM: To investigate whether, under the influence of pol-ypectomy, the incidence of adenoma decreases with age. METHODS: Consecutive patients with colonic adenomas identified at index colonoscopy were retrospectively selected if they had undergone three or more complete colonoscopies, at least 24 mo apart.Patients who had any first-degree relative with colorectal cancer were excluded. Data regarding number of adenomas at each colonoscopy, their location, size and histological classification were recorded. The monthly incidence density of adenomas after the index examination was estimated for the study population, by using the person-years method. Baseline adenomas were excluded from incidence calculations but their characteristics were correlated with recurrence at follow-up, using the χ 2 test .RESULTS: One hundred and fifty-six patients were included (109 male, mean age at index colonoscopy 56.8 ± 10.3 years), with follow-up that ranged from 48 to 232 mo.No significant correlations were displayed betw een the number, the presence of villous component, or the size of adenomas at index colonoscopy and the presence of adenomas at subsequent colonoscopies (P = 0.49, 0.12 and 0.78, respectively). The incidence of colonic adenomas was observed to decay from 1.4% person-months at the beginning of the study to values ​​close to 0%, at 12 years after index colonoscopy. CONCLUSION: Our results suggest the sporadic formation of adenomas occurs within a discrete period and that, when these adenomas are removed, all neoplasia- prone clones may be extinguished.