[Effect of side-to-end anastomosis on postoperative bowel function in rectal cancer surgery: a prospective single-center randomized controlled trial].

Objective: To compare bowel function 12 months after surgery between side-to-end anastomosis (SEA) and end-to-end anastomosis (EEA) groups of patients who had undergone rectal cancer resection. Methods: This single-center, prospective, open-label, phase III randomized controlled trial was approved by the Ethics Committee of Peking University People's Hospital (2018PHB040-01) and registered at ClinicalTrials. org (NCT03669237). Inclusion criteria were as follows: (1) histologically confirmed rectal adenocarcinoma; (2) tumor located 0 to 12 cm from the anal verge; (3) age≥18 years; and (4) planned R0 resection with primary reconstruction. Exclusion criteria included: (1) emergency surgery; (2) cognitive impairment; (3) non-primary anastomosis; (4) history of left-sided colonic or anorectal surgery; and (5) preexisting chronic defecation dysfunction. Eligible rectal cancer patients scheduled for elective sphincter-preserving surgery at Peking University People's Hospital were prospectively enrolled between October 2018 and March 2021 and randomly assigned to either the EEA group or the SEA group via computer-generated numbers prior to entering the operating room. All patients underwent standard radical tumor resection. Bowel function was evaluated by the low anterior resection syndrome (LARS) questionnaire. It consists of five single-choice questions and yields a total score ranging from 0 to 42. Defecation function is categorized into three levels: no LARS (0-20 points), minor LARS (21-29 points), and major LARS (30-42 points). The primary endpoint was the LARS score 12 months after surgery. Secondary endpoints included LARS scores from 1 to 11 months and during long-term follow-up(>12 months). The final follow-up was completed in July 2022. All randomized patients were included in the intention-to-treat set (ITTS). The full analysis set (FAS) was defined as ITTS patients with valid outcome data. All primary statistical analyses were performed in the FAS, and results were further compared in the per-protocol set (PPS) based on the actual treatment received. Results: A total of 323 patients underwent eligibility assessment, of whom 71 did not meet the inclusion criteria and 52 declined to participate. Ultimately, 200 patients were randomized. Median age was 64 years and 85 were women. The SEA and EEA groups comprised 102 and 98 patients, respectively. A total of 181 patients (90.5%) were included in the FAS, and 170 (85.0%) were included in the PPS. Among these, the 12-month LARS score was evaluated in 178 patients (98.3%) in the FAS and in 167 (98.2%) in the PPS. Median LARS score at 1-12 months were significantly lower in the SEA group in both the FAS dataset [12 months:8 (interquartile range [IQR], 0-22) vs. 14 (IQR, 8-29); Z=2.687, P=0.007] and the PPS dataset [12 months: 8 (IQR, 0-22) vs. 14 (IQR, 6-29); Z=2.543, P=0.011]. During long-term follow-up, the median LARS score was also significantly lower in the SEA group in the FAS dataset [2 (IQR, 0-4) vs. 11 (IQR, 2-23); Z=2.968, P=0.003] and the PPS dataset [2 (IQR, 0-14) vs. 11 (2, 27); Z=2.687, P=0.007]. Conclusion: Compared with the EEA group, bowel function was superior in the SEA group 1 year after surgery and during long-term follow-up.