Objective: To compare total mesorectal excision (TME) techniques combined with sphincter-sparing procedure in high-risk patients (HRPs).

Background: TME is the standard treatment for rectal cancer, but can be challenging in HRPs. The available surgical approaches must be compared, especially in HRPs.

Methods: Prospective, observational, multicenter trial to compare laparotomy (OTME), laparoscopy (LTME), robotic-assisted surgery (RTME), and transanal surgery (TaTME) in HRPs. The composite primary outcome included circumferential radial margin (CRM) ≥1mm, TME grade II-III, and absence of Clavien-Dindo grade III-IV complications. Three propensity score analyses were performed (LTME vs. RTME, RTME vs. TaTME, LTME vs. TaTME).

Results: 1078 HRPs (75% of men, median body mass index of 27 kg/m2, 50% of tumors in the lower third of the rectum) underwent surgery. The RTME and TaTME groups included patients with more advanced and lower tumors and coloanal anastomosis (P<0.001). Operative time was longer for RTME surgery (P<0.001). Conversion rate was similar for minimally invasive procedures (4.5%). The global R0 resection rate was 96% without difference among techniques. The primary outcome rates were 82.4%, 64.3%, 74.7%, and 80.3% for LTME, OTME, RTME, and TaTME, respectively. None achieved the expected success rate (85%), and propensity score analyses found no differences. Operative results were similar between high- and low-volume inclusion centers only for RTME.

Conclusions: The RESET trial yielded high-quality results despite focusing on HRPs. Minimally invasive procedures showed similar sphincter-sparing procedure outcomes, but LTME included patients with more favorable tumors.