Low risk of local recurrence after a successful en bloc Endoscopic Submucosal Dissection for non-invasive colorectal lesions with positive horizontal resection margins(R-ESD study)

BACKGROUND : During endoscopic submucosal dissection (ESD), the normal mucosa is cut under constant optical control. We studied whether a positive horizontal resection margin after a complete en bloc ESD predicts local recurrence. METHODS:  In this European multicenter cohort study, patients with a complete en bloc colorectal ESD were selected from prospective registries. Cases were defined by a horizontal resection margin that was positive or indeterminate for dysplasia (HM1), whereas controls had a free resection margin (HM0). Low risk lesions with submucosal invasion (T1) and margins free of carcinoma were analyzed separately. The main outcome was local recurrence. RESULTS:  From 928 consecutive ESDs (2011-2020), 354 patients (40 % female; mean age 67 years, median follow-up 23.6 months), with 308 noninvasive lesions and 46 T1 lesions, were included. The recurrence rate for noninvasive lesions was 1/212 (0.5 %; 95 %CI 0.02 %-2.6 %) for HM0 vs. 2/96 (2.1 %; 95 %CI 0.57 %-7.3 %) for HM1. The recurrence rate for T1 lesions was 1/38 (2.6 %; 95 %CI 0.14 %-13.5 %) for HM0 vs. 2/8 (25 %; 95 %CI 7.2 %-59.1 %) for HM1. CONCLUSION:  A positive horizontal resection margin after an en bloc ESD for noninvasive lesions is associated with a marginal nonsignificant increase in the local recurrence rate, equal to an ESD with clear horizontal margins. This could not be confirmed for T1 lesions.