Impact of Obesity on Postoperative Outcomes in Transanal Total Mesorectal Excision for Rectal Cancer

BACKGROUND: Transanal total mesorectal excision (taTME) has been increasingly adopted in the curative resection of low rectal cancer. Obesity is a known risk factor for conversion and morbidity during laparoscopic and robotic TME. OBJECTIVE: We sought to compare short-term postoperative and pathologic outcomes and long-term oncologic outcomes of transanal total mesorectal excision between non-obese vs. obese patients across high-volume rectal cancer centers in the United States. DESIGN: Retrospective cohort study. SETTINGS: Eight tertiary centers in the United States of America. PATIENTS: Eligible patients underwent transanal total mesorectal excision for curative resection of primary rectal adenocarcinoma between November 2011 and June 2020. MAIN OUTCOME MEASURES: Intraoperative complications, 30-day postoperative complications, local recurrence, distant recurrence, overall survival, disease-free survival. RESULTS: A total of 390 transanal total mesorectal excision procedures were performed in 271 (69.5%) non-obese (BMI < 30 kg/m 2 ) and 120 (30.5%) obese (BMI ≥ 30 kg/m 2 ) patients with a median BMI of 27.4 kg/m 2 (IQR 24.1–31.0). The median follow-up was 29 months (IQR 14-44 months). There were no significant differences in tumor stage or neoadjuvant treatment across groups. Tumors were located ≤ 6cm from the anal verge in 60.6% of patients. Operative time was longer in the obese group, with no significant differences in conversion rates or intraoperative complications. No significant differences in postoperative complications, including Clavien-Dindo grade ≥3 complications, anastomotic complications or reoperation rates were noted between non-obese and obese cohorts. At a median follow-up of 29 months, local recurrence, overall survival, and disease-free survival were comparable between the groups, while obese patients had a significantly lower rate of distant recurrence than non-obese patients. LIMITATIONS: Retrospective design, short median follow up time. CONCLUSIONS: In this multicenter retrospective study, transanal total mesorectal excision resulted in similar conversion and morbidity rates among obese and non-obese patients. Obesity was associated with a significantly lower 3-year distant recurrence with no differences in other mid-term oncologic outcomes.