Impact of Surveillance Colonoscopy Timing on Colorectal Cancer Incidence After Advanced Adenoma Resection

Index colonoscopy findings can affect surveillance decisions that have an impact on the future risk of colorectal cancer (CRC). However, the effectiveness of surveillance colonoscopy in reducing CRC risk remains unclear. The aim of this study was to evaluate whether the timing of the first surveillance colonoscopy affected CRC incidence rates.

We conducted a retrospective cohort study at 2 community endoscopy clinics between 2005 and 2021, including 20,397 individuals. Based on the findings at index colonoscopy, we categorized into 4 groups: advanced adenoma (AA), ≥3 non-AAs, 1-2 non-AAs, and no adenoma. We compared the cumulative incidence of CRC among these groups, focusing on whether the first surveillance interval was less than or greater than 3 years after index colonoscopy.

Index colonoscopy findings identified 11,601 subjects with no adenoma, 5,288 with 1-2 non-AA, 1,484 with ≥3 non-AA, and 2,024 with AA. There were 50 cases of CRC: 23 in the no adenoma, 10 in the 1-2 non-AA, 6 in the ≥3 non-AA, and 11 in the AA group. First surveillance after 3 years was associated with a higher incidence of subsequent CRC in the AA group (hazard ratio 3.49, 95% confidence interval 1.06-11.46, P = 0.04).

In the AA group, surveillance colonoscopy within 3 years was associated with a lower risk of CRC. These findings suggest that a first surveillance within 3 years is particularly effective in subjects with AA.