Underwater EMR for nonpedunculated colorectal lesions

We read with great interest the study by Lenz et al.1Lenz L. Martins B. Andrade de Paulo G. et al.Underwater versus conventional EMR for nonpedunculated colorectal lesions: a randomized clinical trial.Gastrointest Endosc. 2023; 97: 549-558Abstract Full Text Full Text PDF Scopus (4) Google Scholar This study provides new evidence for the clinical use of underwater EMR (UEMR) compared with conventional EMR (CEMR) in the resection of colorectal lesions. However, we do have some comments. This study reported the recurrence rate (RR) as a primary outcome measure and concluded that UEMR had a lower RR compared with CEMR. It is worth noting that most lesions included were intermediate size (10-19 mm), and the RR did not differ significantly between the subgroups at this lesion size interval. The difference was mainly found in the small sample subgroup (lesion size 20-40 mm). The results obtained from a small sample subgroup analysis should not be generalized to draw a complete conclusion about the comparison between the 2 groups. Furthermore, the RR of CEMR in this study (35.7%) was far higher than that of 14% reported in previous studies,2Chandan S. Facciorusso A. Ramai D. et al.Snare tip soft coagulation (STSC) after endoscopic mucosal resection (EMR) of large (> 20 mm) on-pedunculated colorectal polyps: a systematic review and meta-analysis.Endosc Int Open. 2022; 10: E74-E81Crossref PubMed Scopus (8) Google Scholar,3Hassan C. Repici A. Sharma P. et al.Efficacy and safety of endoscopic resection of large colorectal polyps: a systematic review and meta-analysis.Gut. 2016; 65: 806-820Crossref PubMed Scopus (228) Google Scholar which was the main reason for the statistical difference. This phenomenon should be considered and explained. Recent studies have indicated that UEMR has a higher en bloc resection rate (ERR) than does CEMR.4Nagl S. Ebigbo A. Goelder S.K. et al.Underwater vs conventional endoscopic mucosal resection of large sessile or flat colorectal polyps: a prospective randomized controlled trial.Gastroenterology. 2021; 161: 1460-14674.e1Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar,5Yamashina T. Hanaoka N. Setoyama T. et al.Efficacy of underwater endoscopic mucosal resection for nonpedunculated colorectal polyps: a systematic review and meta-analysis.Cureus. 2021; 13e17261Google Scholar One of the most likely explanations for the lower RR of UEMR is the transformation of its higher ERR.4Nagl S. Ebigbo A. Goelder S.K. et al.Underwater vs conventional endoscopic mucosal resection of large sessile or flat colorectal polyps: a prospective randomized controlled trial.Gastroenterology. 2021; 161: 1460-14674.e1Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar,6Yamasaki Y. Uedo N. Akamatsu T. et al.Nonrecurrence rate of underwater EMR for ≤20-mm nonampullary duodenal adenomas: a multicenter prospective study (D-UEMR study).Clin Gastroenterol Hepatol. 2022; 20: 1010-1018.e3Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar There was no statistical difference in ERR between groups in this study, although this rate is obviously higher for UEMR (60.6%). On the basis of previous published studies, the distinction of lesion size (≥20 mm or <20 mm) may further clarify the possible difference in this indicator. The current study did not use resection time as of the outcome measures. Previous studies have shown inconsistent results in assessing differences in this measure between the groups.5Yamashina T. Hanaoka N. Setoyama T. et al.Efficacy of underwater endoscopic mucosal resection for nonpedunculated colorectal polyps: a systematic review and meta-analysis.Cureus. 2021; 13e17261Google Scholar,7Chandan S. Khan S.R. Kumar A. et al.Efficacy and histologic accuracy of underwater versus conventional endoscopic mucosal resection for large (>20 mm) colorectal polyps: a comparative review and meta-analysis.Gastrointest Endosc. 2021; 94: 471-482.e9Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar Therefore, further data from randomized controlled trials are urgently needed. The evaluation of the efficiency of UEMR will be useful to assist the clinical selection of resection methods. We kindly hope that the authors may provide further data to increase the understanding of this issue. All authors disclosed no financial relationships.