The Effectiveness and Safety of Endoscopic Intermuscular Dissection for the Treatment of Rectal Gastrointestinal Stromal Tumors: A Pilot Feasibility Study

Background/Objectives: Rectal gastrointestinal stromal tumors (GISTs) near the dentate line (DL) present significant surgical challenges due to anatomical constraints and difficulty preserving anal function. Endoscopic intermuscular dissection (EID) is a viable alternative in these cases. Methods: We retrospectively reviewed the medical records of patients who underwent EIDs for rectal GISTs near the DL between January 2015 and December 2023. The primary outcomes assessed were procedural efficacy—measured by en bloc and complete resection rates—and safety, evaluated regarding delayed bleeding, perforation, and tumor recurrence. Results: In total, 10 patients underwent rectal GIST EIDs. The mean tumor size, procedure time, and resection speed were 25.70 ± 14.09 mm, 81.30 ± 46.20 min, and 16.91 ± 9.94 mm2/min, respectively. The en bloc and complete resection rates were 100% and 70%, respectively. Compared with endoscopic submucosal dissection (ESD) for rectal epithelial lesions, there were no significant differences in procedure times (81.30 ± 46.20 min vs. 76.50 ± 32.42 min, p = 0.758) or complete resection rates (70% vs. 95%, p = 0.095). Regarding safety, delayed bleeding (10% vs. 10%, p = 1.000) and perforation (10% vs. 0%, p = 0.333) rates did not differ significantly between the two groups. During a median 36-month follow-up, one recurrence occurred in a patient with a high-risk GIST. Conclusions: EID for rectal GISTs near the DL appears to be a feasible and potentially safe treatment option in carefully selected patients. It may represent a less invasive alternative to surgery, particularly when preservation of anal function is a priority. Nevertheless, validation in larger prospective studies is required.