The U.K. guidelines for risk stratification after colon polypectomy differ from the U.S. guidelines in 2 ways: the U.K. guidelines consider ≥5 adenomas as high risk and do not consider histology (villous or high-grade dysplasia) in the assessment. Thus, we aimed to investigate the risk of advanced colorectal neoplasm (CRN) by categorized risk groups, considering both ≥5 adenomas and histology.

A total of 2570 patients with ≥1 adenoma at index colonoscopy were included. The patients were divided into 6 groups: group 1, 1 to 2 non-advanced adenomas (non-AAs) ≥10 mm or high-grade dysplasia or villous adenoma; group 1A, 1 to 2 adenomas with ≥1 advanced adenoma (AA); group 2, 3 to 4 non-AAs; group 2A, 3 to 4 adenomas with ≥1 AA; group 3, ≥5 non-AAs; and group 3A, ≥5 adenomas with ≥1 AA. The risk of advanced CRN at 3 years was compared among the 6 groups.

Group 3A showed a higher risk of advanced CRN (9.6%) than group 3 (4.5%; P = .03) and group 1A (4.6%; P < .001). The risk of advanced CRN in group 3 (4.5%) showed no difference compared with group 1A (4.6%; P = .91) or group 2A (6.8%; P = .25). There was no difference between group 1 and group 2 in the risk of advanced CRN (1.7% vs 2.2%; P = .22). More than 1 AA at index colonoscopy was an independent risk factor for advanced CRN.

More-intensive surveillance than the 3-year interval for patients with ≥5 adenomas with ≥1 AA and less-intensive surveillance than the 3-year and 1-year intervals for those with 3 to 4 non-AAs and ≥5 non-AAs, respectively, might be suggested.