CHICAGO—Underwater endoscopic mucosal resection conveys numerous advantages over the conventional approach for resection of colorectal polyps, according to a meta-analysis presented at Digestive Disease Week 2023.

“We found that for all lesions—irrespective of their size—underwater endoscopic mucosal resection outperforms conventional EMR in terms of en bloc resection, R0 resection and rate of polyp recurrence,” said lead investigator Saurabh Chandan, MD, an assistant professor of gastroenterology at Creighton University School of Medicine, in Omaha, Nebraska.

The data are somewhat less clear for lesions larger than 20 mm, he added. “I would say that [underwater] EMR is comparable to [conventional] EMR, and perhaps somewhat more favorable.”

Dr. Chandan and his co-investigators conducted a systematic review and meta-analysis comparing outcomes of the two techniques, assessing data of successful R0, en bloc and piecemeal resections from prospective randomized controlled trials published by November 2022 (abstract Sa1715). With results from seven randomized controlled trials, the meta-analysis included 865 resections performed with underwater EMR and 826 resections with conventional EMR, of which 177 and 192, respectively, involved polyps larger than 20 mm.

The overall pooled rate of successful R0 resection was higher with underwater EMR vs conventional EMR (58.1% vs. 44.6%, respectively). However, this difference just missed statistical significance, Dr. Chandan said.

Of note, multiple other outcomes were significantly improved with this approach. Tests of heterogeneity varied according to the outcome, he said. While they found the pooled rate of en bloc resection significantly higher with underwater EMR, the difference was not statistically significant for polyps greater than 20 mm. Piecemeal resection was significantly lower in the underwater group than in the conventional group (19.2% vs. 33.8%, respectively).

Overall pooled rates of perforation, immediate bleeding and delayed bleeding were comparable between the approaches, as was resection time.

Asked to comment, Felix W. Leung, MD, a professor-in-residence at the University of California, Los Angeles David Geffen School of Medicine, said in the past few years, randomized trials have compared these approaches, yielding findings that suggest “the newcomer offers better results” and the current meta-analysis “confirms that.”

There was a strong trend favoring underwater EMR in achieving R0 resection, and the lack of statistical significance for this difference may be due to the overall small sample size, he suggested.

“Nonetheless,” Dr. Leung said, “long-term follow-up addressing the question of whether patients managed by [underwater] EMR will have a lower rate of interval cancers deserves to be considered.”

—Caroline Helwick

Drs. Chandan and Leung reported no relevant financial disclosures.