Efficacy and safety of endoscopic submucosal dissection for rectal tumors with or without dentate line involvement: a propensity score matching analysis.

OBJECTIVE: To evaluate the technical feasibility, safety, and therapeutic outcomes of endoscopic submucosal dissection (ESD) for rectal tumors extending to the dentate line (RTDLs) compared with non-RTDLs using propensity score matching (PSM). METHODS: We retrospectively reviewed 127 patients with rectal tumors treated with ESD at two tertiary centers from November 2012 to December 2023 (51 RTDLs, 76 non-RTDLs). A 1:1 PSM based on age, sex, and lesion diameter yielded 51 matched pairs (102 patients in total). Procedural parameters, pathological outcomes (classified as low-grade dysplasia (LGD), high-grade dysplasia (HGD), and adenocarcinoma), postoperative complications, and long-term oncological outcomes were systematically analyzed. RESULTS: Following 1:1 PSM, baseline characteristics were well balanced between the non-RTDLs and RTDLs groups (P>0.05). En bloc resection was achieved in 100.0% of cases in both groups. R0 resection rates were comparable between the non-RTDLs and RTDLs groups (98.04% vs. 96.08%, P>0.999). However, the RTDLs group required a significantly longer mean ESD procedure duration (99.3 ± 72.8 min vs. 56.0 ± 52.9 min, P = 0.002) and demonstrated lower dissection speed (5.7 ± 6.5 min/cm2 vs. 3.1 ± 2.4 min/cm2, P = 0.010). Pathologically, precancerous neoplasms predominated in both groups, with HGD accounting for 47.1% in non-RTDLs and 51.0% in RTDLs; invasive adenocarcinoma accounted for 9.8% and 15.7%, respectively. Postoperative anal pain was significantly more frequent in the RTDLs group (25.6% vs. 5.4%, P = 0.025). Numerical increases in delayed bleeding (7.7% vs. 0.0%, P = 0.241) and rectal stenosis (17.9% vs. 2.7%, P = 0.056) were observed in the RTDLs group, without reaching statistical significance. No perforations, local recurrences, distant metastases, or disease-related deaths occurred during follow-up (P>0.999). CONCLUSION: ESD is a safe and effective organ-preserving treatment for rectal tumors extending to the dentate line, achieving excellent en bloc and R0 resection rates comparable to non-RTDLs. However, RTDLs present substantial technical complexity, resulting in longer procedure times, lower dissection efficiency, and increased risk of postoperative anal pain. Careful preoperative planning, endoscopist expertise, and close postoperative surveillance are essential when managing RTDLs.