Short-Term Outcomes of Transanal Total Mesorectal Excision for Rectal Cancer: A Multicenter Propensity Score-Matched Analysis Comparing Patients With and Without Preoperative Neoadjuvant Therapy.

Aim: To evaluate the association between preoperative neoadjuvant therapy and short-term outcomes of transanal total mesorectal excision for rectal cancer.

Methods: We retrospectively analyzed patients who underwent transanal total mesorectal excision at 26 Japanese institutions between 2012 and 2019. Patients who received neoadjuvant therapy were matched 1:1 with patients who did not. Perioperative, postoperative, and pathological outcomes were compared.

Results: After matching, 294 patients (147 per group) were analyzed. Operative time was longer in the neoadjuvant therapy group than in the non-neoadjuvant therapy group (median, 510.0 vs. 382.0 min), with an adjusted mean difference of 129.25 min (95% CI, 87.90-170.59; p < 0.001). Clavien-Dindo grade ≥ III complications occurred in 18/147 patients (12.2%) without neoadjuvant therapy and 16/147 (10.9%) with neoadjuvant therapy (adjusted OR, 0.90; 95% CI, 0.44-1.85; p = 0.769). Full-cohort conventional and Firth logistic analyses and marginal standardization likewise did not identify a statistically significant association. Neoadjuvant therapy remained associated with longer operative time after adjustment for operative procedure, lateral pelvic lymph node dissection, and abdominal approach. Resection-margin involvement did not differ significantly between groups.

Conclusion: Neoadjuvant therapy was associated with longer operative time during transanal total mesorectal excision, whereas no statistically significant association with severe postoperative morbidity was detected. Sensitivity analyses likewise did not identify a statistically significant association, supporting the technical feasibility of transanal total mesorectal excision after neoadjuvant therapy in experienced centers.