S1280 Underwater vs Conventional Endoscopic Mucosal Resection for Superficial Non-Ampullary Duodenal Epithelial Tumors ≤20 Mm in Size: An Updated Systematic Review and Meta-Analysis

Introduction: Endoscopic mucosal resection (EMR) is the method of choice for resection of superficial non-ampullary duodenal epithelial tumors (SNADETs) ≤20 mm in size. Underwater EMR (UEMR), unlike conventional EMR (CEMR), is a simpler procedure that does not require submucosal injection. Results of studies comparing UEMR and CEMR show mixed results. We conducted a systematic review and meta-analysis aiming to compare the safety and efficacy of UEMR and CEMR for resection of SNADETs ≤20 mm. Methods: A comprehensive search of MEDLINE, EMBASE, and Scopus was performed through April 2025 to identify studies comparing UEMR and CEMR for SNADETs ≤20 mm. Outcomes assessed included rates of en bloc and R0 resection, delayed bleeding, perforation, and recurrence. Pooled effect estimates were calculated using a random-effects model and expressed as odds ratios (OR) or mean difference (MD) with 95% confidence intervals (CI). Heterogeneity was evaluated using the I² statistic. Results: A total of 7 retrospective studies and 921 SNADET lesions were included. UEMR was used in 413 lesions, while CEMR was used in 508 lesions. Six studies were set in Japan, while 1 was multi-center and set in 5 European countries. There was no difference in the odds of en bloc resection ([odds ratio] OR 1.26; 95% CI [0.65, 2.43]; P = 0.5) and R0 resection (OR 1.21; 95% CI [0.68, 2.13]; P = 0.52) in the UEMR compared to the CEMR group. Mean procedure time was significantly shorter in the UEMR group (MD -3.54; 95% CI [-6.67, -0.41]; P = 0.03). There was no difference demonstrated in the odds of perforation following resection (OR 0.43; 95% [0.07, 2.65]; P = 0.36), delayed bleeding (OR 0.92; 95% CI [0.20, 4.16]; P = 0.91) and recurrence (OR 0.65; 95% CI [0.27, 1.59]; P = 0.35). Conclusion: Our meta-analysis shows that the resection of SNADETs ≤20 mm with UEMR carries equal rates of clinical outcomes, including adverse events compared to CEMR while having shorter procedure times. For these lesions, UEMR may be a faster alternative to CEMR with equal efficacy, but further large-scale prospective studies are needed to better define its role.