Comparison of transanal total mesorectal excision and robotic total mesorectal excision for rectal cancer: an inverse probability of treatment weighting analysis.

BACKGROUND: Both transanal total mesorectal excision (TaTME) and robotic total mesorectal excision (robotic TME) have been developed to optimize mesorectal dissection quality in rectal cancer surgery. However, current evidence remains inconclusive regarding the comparative advantages between these two minimally invasive approaches. MATERIALS AND METHODS: Patients who underwent curative TaTME or robotic TME for rectal cancer at our institution from 2015 to 2021 were retrospectively reviewed. The primary outcomes were circumferential resection margin (CRM) involvement and oncological outcomes (local recurrence, disease-free survival, and overall survival). Secondary outcomes included operative time, blood loss, conversion rate, postoperative complications, and functional recovery. To adjust for baseline differences, inverse probability of treatment weighting (IPTW) was employed. RESULTS: A total of 174 patients were included in the final analysis, comprising 110 who underwent TaTME and 64 who underwent robotic TME. While operative duration was comparable, the TaTME group exhibited increased intraoperative blood loss and higher rates of diverting stoma (72.6% vs. 51.7%, p < 0.001) and hand-sewn anastomosis (43.6% vs. 24.1%, p < 0.001) than the robotic TME group. Minor complications (Clavien-Dindo grade I) were more frequent in the TaTME group, though major morbidity was similarly low in both cohorts. Pathologically, TaTME was associated with a greater incidence of positive circumferential resection margins (CRM) (6.1% vs. 0%, p = 0.001) and shorter distal margins. Long-term oncological endpoints, including local recurrence, distant metastasis, overall survival, and disease-free survival were statistically similar. CONCLUSIONS: Despite certain technical drawbacks observed in TaTME, such as increased blood loss and CRM positivity, both techniques demonstrated equivalent long-term oncologic safety, indicating their appropriateness in selected patients undergoing rectal cancer resection.