Margin thermal ablation eliminates size as a risk factor for recurrence after piecemeal endoscopic mucosal resection of large non-pedunculated colorectal polyps.

Background: Lesion size is an independent risk factor for recurrence following endoscopic mucosal resection of large (≥20 mm) non-pedunculated colorectal polyps. Post-resection margin thermal ablation (MTA) reduces the risk of recurrence. Its impact on the uncommon larger (≥40 mm) lesions is unknown.

Objective: We sought to analyse the impact of MTA on ≥40 mm lesions in a large, prospective cohort.

Design: A prospective cohort of patients with colorectal polyps ≥20 mm treated with piecemeal endoscopic mucosal resection in an expert tissue resection centre was divided into three phases: 'pre-MTA', July 2009-June 2012; 'MTA-adoption', July 2012-June 2017 and 'standardised-MTA', July 2017-July 2023. Recurrence was defined as adenomatous tissue endoscopically and/or histologically detected at the first surveillance colonoscopy. The primary outcome was the recurrence rate over the three time periods in three size groups: 20-39 mm, 40-59 mm and ≥60 mm.

Results: Over 14 years until July 2023, 1872 sporadic colorectal polyps ≥20 mm in 1872 patients underwent endoscopic mucosal resection (median lesion size 35 mm (IQR 25-45mm)). Of these, 1349 patients underwent surveillance colonoscopy at a median of 6 months (IQR 4-8 months). The overall rates of recurrence in the pre-MTA, MTA-adoption and standardised-MTA phases were 13.5% (n=42/310), 12.6% (n=72/560) and 2.1% (n=10/479), respectively, (p≤0.001). When MTA was applied in the standardised-MTA phase, the rate of recurrence was the same among 20-39 mm (1.5% (3/205)), 40-59 mm (1.6% (3/190)) and ≥60 mm polyps (1.4% (1/73)) (p=1.00).

Conclusion: MTA negates the effect of size on the incidence of recurrence after piecemeal endoscopic mucosal resection of colorectal polyps ≥40 mm.

Trial Registration Number: Australian Colonic Endoscopic Resection cohort (NCT01368289; NCT02000141).