Utility of Transanal Total Mesorectal Excision in Patients with Obesity and with Low and Middle Rectal Cancer: A Single-Center, Retrospective Cohort Study

BACKGROUND: Benefits of transanal total mesorectal excision in patients with obesity remain unclear. Objective: To evaluate the clinical utility of transanal total mesorectal excision in patients with obesity with mid-to-low rectal cancer. Design: Retrospective cohort study. Settings: Single center, between April 2015 and March 2025. Patients: Six hundred eighty-three patients with mid-to-low rectal cancer INTERVENTION: Transanal total mesorectal excision for rectal cancer. MAIN OUTCOME MEASURES: Patients were categorized as nonobese (body mass index < 25.0 kg/m 2 ), obese I (25.0–29.9 kg/m 2 ), and obese II (≥ 30 kg/m 2 ). Surgical and pathological outcomes—conversion to open surgery, sphincter preservation, and resection margin status—were compared. Results with corrected p value < 0.05 were considered significant. RESULTS: Overall, 485 (71%) patients were categorized as nonobese, 159 (23%) as obese I, and 39 (6%) as obese II. Clinicopathological characteristics were similar among the groups. Operative times were longer in the obese I and II groups (218 and 265 vs. 194 min, p < 0.05), with greater blood loss (44 and 90 vs. 39 mL, p < 0.05). Sphincter-preserving surgery was performed as planned in all patients; conversion to open surgery (1.0%, 1.3%, and 0%, p = 0.783) were comparable, whereas anastomotic leakage was more frequent in the obese II group (4.5%, 6.3%, and 15.4%, p = 0.016). The overall circumferential resection margin-positivity rate was 3.4%, with no significant differences among the groups (3.3%, 3.1%, and 5.1%). LIMITATIONS: Single high-volume cancer center with surgeons experienced in transanal total mesorectal excision limits generalizability; lack of comparative cohort limits direct assessment of the efficacy of the approach; the obese II group had few patients; and BMI’s accuracy as a surrogate for visceral fat is limited. CONCLUSIONS: Transanal total mesorectal excision appears to represent a promising strategy for patients with obesity with mid-to-low rectal cancer, offering low conversion and high sphincter preservation rates while maintaining oncologic safety. See Video Abstract .