Transanal Total Mesorectal Excision vs Robotic Total Mesorectal Excision

Both RTME and taTME are innovative surgical techniques with potential advantages in low rectal cancer. Intraoperative conversion rate is a key safety metric. In low rectal cancer, changes in surgical approach not only affect resection outcomes but also sphincter preservation.To date, no clinical studies have directly compared the conversion and complication rates between taTME and RTME in this population. Therefore, the investigators propose to conduct a prospective, randomized, parallel-controlled clinical trial comparing taTME with RTME for low rectal cancer, aiming to provide high-level evidence for surgical decision-making and benefit more patients. The primary indicator in this study is intraoperative conversion rate. Definition in each group as follows: During transanal total mesorectal excision (taTME), if the procedure cannot be completed due to difficulty in transanal operation, conversion to open abdominal surgery is required to complete TME resection, allowing better operative access, organ preservation, and tumor clearance. During robot-assisted total mesorectal excision (rTME), if the transabdominal approach fails to achieve bowel transection or digestive reconstruction, conversion to transanal or open abdominal surgery is required to complete the procedure, ensuring operability, organ preservation, and tumor clearance.

Inclusion criteria

Newly diagnosed patients aged 18-75 years. Pathologically confirmed adenocarcinoma (tubular, papillary, mucinous, or signet-ring). Tumor ≤7 cm from anal verge (MRI or DRE). Clinical stage T1-T3, N+, M0 (AJCC 8th ed.), suitable for sphincter-preserving TME. ASA score I-III.

ECOG performance status 0-1. Informed consent obtained.

• Exclusion Criteria: Synchronous/metachronous colorectal cancers, local recurrence, or distant metastases. Bowel obstruction, perforation, bleeding requiring emergency surgery. Involvement of sphincter or adjacent organs requiring Inter-sphincter Resection (ISR). Poor preoperative anal function/incontinence. IBD or familial adenomatous polyposis (FAP).

Pregnancy or lactation. Severe psychiatric illness. Other malignancies within 5 years. Severe comorbidities or infections making surgery intolerable. Judged unsuitable by investigator.