Impact of en bloc resection on long-term outcomes after endoscopic mucosal resection: a matched cohort study

Background and Aims: Residual or recurrent adenoma (RRA) is the major limitation of piecemeal EMR (p-EMR) for large colonic laterally spreading lesions (LSLs) >= 20 mm. En bloc EMR (e-EMR) has been shown to achieve low rates of RRA but specific procedural and long-term outcomes are unknown. Our aim was to compare long-term outcomes of size-matched LSLs stratified by whether they were resected e-EMR or p-EMR. Methods: Data from a prospective tertiary referral multicenter cohort of large LSLs referred for EMR over a 10-year periodwere analyzed. Outcomes were compared between sized-matched LSLs (20-25mm) resected by p-EMR or e-EMR. Results: Five hundred seventy LSLs met the inclusion criteria of which 259 (45.4%) were resected by e-EMR. The risk of major deep mural injury (DMI) was significantly higher in the e-EMR group (3.5% vs 1.0%, P = .05), whereas rates of other intraprocedural adverse events did not differ significantly. Five of 9 (56%) LSLs, with endoscopic features of submucosal invasion (SMI), resected by e-EMR were saved from surgery. RRA at first surveillance was lower in the e-EMR group (2.0% vs 5.7%, P = .04), but this difference was negated at subsequent surveillance. Rates of surgical referral were not significantly different between the groups at either surveillance interval. Conclusion: When comparing e-EMR against p-EMR for lesions <= 25mm in size of similar morphology in a large prospective multicenter cohort, e-EMR offered no additional advantage for predicted-benign LSLs. However, it was associated with an increased risk of major DMI. Thus, en bloc resection techniques should be reserved for lesions suspicious for invasive disease.