Effectiveness and safety of cold snare polypectomy and cold endoscopic mucosal resection for nonpedunculated colorectal polyps of 10-19 mm: a multicenter observational cohort study.

BACKGROUND : Cold snare polypectomy (CSP) is the standard of care for the resection of small (< 10 mm) colonic polyps. Limited data exist for its efficacy for medium-sized (10-19 mm) nonpedunculated polyps, especially conventional adenomas. This study evaluated the effectiveness and safety of CSP/cold endoscopic mucosal resection (C-EMR) for medium-sized nonpedunculated colonic polyps. METHODS : A prospective multicenter observational study was conducted of all morphologically suitable nonpedunculated colonic polyps of 10-19 mm removed by CSP/C-EMR between May 2018 and June 2021. Once resection was complete, multiple biopsies were taken of the margins circumferentially and centrally. The primary outcome was the incomplete resection rate (IRR), based on residual polyp in these biopsy specimens. Secondary outcomes were recurrence rate at first surveillance colonoscopy and rates of adverse events (AEs). RESULTS : CSP/C-EMR was performed for 350 polyps (median size 15 mm; 266 [76.0 %] Paris 0-IIa classification) in 295 patients. Submucosal injection was used for 87.1 % (n = 305) of polyps. Histology showed 68.6 % adenomas, 26.0 % sessile serrated lesions (SSLs) without dysplasia, 4.0 % SSL with dysplasia, and 1.4 % hyperplastic polyps. The IRRs based on margin or central biopsies being positive were 1.7 % (n = 6) and 0.3 % (n = 1), respectively. The polyp recurrence rate was 1.7 % (n = 4) at first surveillance colonoscopy - completed for 65.4 % (n = 229) of polyps at a median interval of 9.7 months. AEs occurred in 3.4 % (n = 10) of patients: four with post-polypectomy pain; three self-limiting post-polypectomy bleeds; two post-polypectomy-syndrome-like presentations; and one intraprocedural bleed treated with clips. There were no perforations. CONCLUSION : CSP/C-EMR for morphologically suitable nonpedunculated colonic polyps of 10-19 mm is effective and safe, including for conventional adenomas. Rates of incomplete resection and recurrence were low, with few AEs. Studies directly comparing this method with hot snare resection are required.