Background and aims: EMR is the standard of care for the management of large (≥20mm) non-pedunculated colonic polyps (LNPCPs). However, its efficacy and cost effectiveness, are limited by recurrence and the necessity for scheduled surveillance. Consequently, current surveillance intervals are conservative. Margin thermal ablation (MTA) after EMR for LNPCPs has dramatically reduced the incidence of recurrence at first surveillance colonoscopy at six-months (SC1). If this effect is durable, then subsequent surveillance intervals in patients who have been cleared of synchronous polyps could be substantially lengthened. We prospectively evaluated long-term surveillance outcomes in a cohort of LNPCPs that have undergone MTA.

Methods: Consecutive patients with LNPCPs undergoing EMR and MTA from four academic endoscopy centres were prospectively recruited. All patients that underwent successful endoscopic resection received SC1 six months post resection. EMR scars were carefully evaluated with high-definition white light, narrow band imaging with near focus and biopsy. In the absence of recurrence, second surveillance (SC2) colonoscopy was conducted at a subsequent interval of 12 months with the scar evaluation process repeated. The primary outcome was recurrence at SC2 in all LNPCPs with a recurrence-free scar at SC1.

Results: 1183 LNPCPs referred for EMR were enrolled over 90 months until October 2022. Following exclusions (Figure 1), 1044 LNPCPs underwent EMR with complete MTA. 775 LNPCPs underwent SC1 at a mean interval of 6.3 months (95%CI 6.0-6.6). 34 additional synchronous LNPCPs were cleared at this procedure. 23/775 (3%) (95%CI 1.9-4.4%) LNPCPs demonstrated recurrence. 416 LNPCPs free of recurrence at SC1 (median size 35mm) underwent SC2 at a mean interval of 23.3 months (95%CI 22.2-24.4) after the index EMR. 415 demonstrated a bland scar without recurrence. Only one recurrence occurred (0.2% 95%CI 0-1.3%), related to a 0-IIa+Is 20mm granular TVA located on the ileocaecal valve.

Conclusion: LNPCPs that have undergone successful EMR with MTA and are free of recurrence at SC1 are very unlikely to develop recurrence in subsequent surveillance out to 2 years. Following EMR of LNPCPs with MTA, patients who are cleared of synchronous neoplasia and demonstrate no recurrence after careful scar examination, can potentially undergo next surveillance in 3-5 years. Such an approach would reduce costs and enhance patient compliance.

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