Do surveillance intervals in patients with more than five adenomas at index colonoscopy be shorter than those in patients with three to four adenomas? A Korean Association for the Study of Intestinal Disease study

Background and Aim: There is controversy about the surveillance interval after colonoscopy when 5–10 adenomas have been found on index colonoscopy. This study aimed to investigate the risk of colorectal neoplasm (CRN) according to the number of adenomas at index colonoscopy. Methods: A retrospective, multicenter study was conducted at 10 university hospitals in Korea. We included 1394 patients with ≥ 3 adenomas at index colonoscopy. The risk of advanced CRN was compared according to the number of adenomas (intermediate risk group, 3–4 small adenomas or at least one ≥ 10 mm, and high risk group, ≥ 5 small adenomas or ≥ 3 at least one ≥ 10 mm). Results: Overall, 164 (11.8%) developed an advanced CRN after a mean of 4.0 years from baseline colonoscopy. The 3-year and 5-year risk of advanced CRN was 2.1% (95% CI 2.09–2.11) and 14.4% (95% CI 14.36–14.44) in intermediate risk group and 3.2% (95% CI 3.19–3.21) and 23.3% (95% CI 19.15–19.25) in high risk group (P = 0.01). Having ≥ 5 adenomas (OR = 1.57, 95% CI 1.11–2.23, P = 0.01) detected at index colonoscopy was a significant risk factor for developing advanced CRN. Conclusions: Although risk of advanced CRN in patients with 5–10 adenomas was significantly higher than that in patients with 3–4 adenomas, the cumulative risk at 3 years was low at 3.2%. Thus, we suggest that a 3-year surveillance interval might be appropriate for the patients with 5–10 adenomas, and further prospective studies are needed to investigate whether more intensive surveillance is needed in this group.