# Comparison of Endoscopic Therapies for Small Rectal Neuroendocrine Tumors: Endoscopic Muscularis Superficialis Dissection Versus Endoscopic Submucosal Dissection

## TL;DR

A new endoscopic technique called EMSD was found to be more effective than ESD in completely removing small rectal neuroendocrine tumors, reducing the need for repeat procedures.

## Contribution

The study introduces endoscopic muscularis superficialis dissection (EMSD) as a novel endoscopic technique for treating rectal neuroendocrine tumors.

## Key findings

- EMSD achieved 100% complete vertical margin resection compared to 69.8% with ESD.
- EMSD had a 100% R0 resection rate versus 67.9% for ESD.
- EMSD and ESD had similar procedure times and hospital stays, with minimal complications.

## Abstract

Rectal neuroendocrine tumors (rNETs) often exhibit submucosal tumor‐like growth. While endoscopic submucosal dissection (ESD) is widely used, it carries a risk of positive vertical margins, often necessitating repeated surveillance and imposing both financial and psychological burdens on patients. To address this limitation, we developed endoscopic muscularis superficialis dissection (EMSD), a technique involving controlled dissection into the superficial muscularis propria layer to improve complete resection rates. This study aimed to compare the therapeutic outcomes of EMSD and ESD for small rNETs.

This retrospective study enrolled 82 patients (88 rNETs) undergoing ESD or EMSD between May 2019 and June 2025. Primary outcomes included complete resection rates, complication rates, and postoperative hospital stay.

The study analyzed 35 lesions treated with EMSD and 53 with ESD. Both groups had similar tumor characteristics. Compared to ESD, EMSD achieved significantly higher rates of both complete vertical margin resection (100% vs. 69.8%, p < 0.001) and R0 resection (100% vs. 67.9%, p < 0.001). However, there were no significant differences in procedure time (47.0 ± 17.0 min vs. 40.0 ± 9.5 min; p = 0.070) and postoperative hospital stay (4.0 ± 1.5 days vs. 4.0 ± 1.0 days; p = 0.676). Postoperative bleeding occurred in 1 EMSD patient (2.9%), which was managed endoscopically. No other bleeding or perforation cases occurred.

Compared with ESD, EMSD achieved superior performance in the resection of rNENs ≤ 10 mm in diameter regardless of submucosal invasion depth.