Safety of first surveillance colonoscopy at 12 months after piecemeal endoscopic mucosal resection of large non-pedunculated colorectal lesions

Background and Aims After piecemeal endoscopic mucosal resection (pEMR) of nonpedunculated colorectal lesions ≥ 20 mm, guidelines recommend first endoscopic surveillance at 6 months. However, initial surveillance at 12 months may be adequate for selected low-risk lesions, and could save the cost, risk and inconvenience of one surveillance examination. Methods We retrospectively examined a prospectively collected database of all colorectal lesions referred to our center for endoscopic resection between August 2019 and April 2023. We report recurrence rates of colorectal lesions ≥ 20 mm removed by pEMR who were assigned to 6-month first surveillance or assigned to 12-month first surveillance (or assigned to 6-month but did not return until after 10 months). Results There were 561 nonpedunculated lesions ≥ 20 mm that underwent first follow-up, including 490 lesions in 443 patients assigned to 6-month, and 71 lesions in 65 patients assigned to 12-month surveillance. Lesions assigned to 12-month surveillance were smaller (mean size 25.9 ± 6.1mm vs. 37.0 ± 17.4mm), more likely serrated (63.4% vs. 9.6%), and more often removed by cold pEMR (74.6% vs 20.4%). Twenty-nine lesions in 24 patients assigned 6-month surveillance presented after 10 months and their recurrence data were included in the group assigned 12-month surveillance.Overall recurrence rates at 6 months and 12 months were 10.0% (46/461) and 9.0% (9/100), respectively. Mean recurrence sizes at 6 and 12 months were 10.9 ± 6.2mm and 4.2 ± 1.9mm, respectively. One patient in the 6-month surveillance group had cancer at the pEMR site, but no other recurrences at 6 or 12 months had either cancer or high-grade dysplasia. Conclusion Twelve-month surveillance appears acceptable for selected colorectal lesions ≥ 20 mm removed by pEMR. A randomized trial comparing initial 6-month to 12-month surveillance is warranted for selected lesions.