This is a multicenter, superior, randomized controlled trial designed to compare Robotic-assisted total mesorectal excision (RATME) and laparoscopic-assisted total mesorectal excision (LATME) for middle and low rectal cancer. The primary endpoint is the incidence of intersphincteric resection (ISR). The secondary outcomes are coloanal anastomosis (CAA), conversion to open, conversion to transanal TME (TaTME), incidence of abdominoperineal resection (APR), postoperative morbidity and mortality within 30 days after surgery, pathological outcomes, long-term survival outcomes, functional outcomes, and quality of life.

Robotic-assisted total mesorectal excision (RATME) has been gradually applied by colorectal surgeons. Most surgeons consider RATME a safe method and believe it can facilitate total mesorectal excision (TME) in rectal cancer, especially middle and low rectal cancer with a narrow pelvis. Therefore, this trial investigates whether RATME has technical advantages and increase intersphincteric resection rate compared with laparoscopic-assisted TME (LATME) in middle and low rectal cancer.

This is a multicenter, superior, randomized controlled trial designed to compare RATME and LATME for middle and low rectal cancer. The primary endpoint is the incidence of intersphincteric resection (ISR). The secondary outcomes are coloanal anastomosis (CAA), conversion to open, conversion to transanal TME (TaTME), incidence of abdominoperineal resection (APR), postoperative morbidity and mortality within 30 days after surgery, pathological outcomes, long-term survival outcomes, functional outcomes, and quality of life. In addition, certain measures will be conducted to ensure quality and safety, including centralized photography review and semiannual assessment.

Inclusion Criteria:

1. male patients diagnosed with rectal cancer by pathological biopsy;
2. abdominal contrast-enhanced and chest computed tomography (CT) or positron emission tomography-computed tomography (PET-CT) revealed no distal metastasis;
3. Preoperative rectal magnetic resistance (MR) evaluation showed that the tumor was located at or below the peritoneal reflux plane, and at least 1cm above the anal sphincter groove, and did not invade the external anal sphincter;
4. Tumors located above the hiatus of levator ani muscle were evaluated by magnetic resonance imaging as cT1-3, cN0-1, M0, and MRF (-); The tumors located below the hiatus of levator ani muscle were evaluated by magnetic resonance imaging as cT1-2, cN0-1, M0, and MRF (-). After neoadjuvant treatment, the tumor above the hiatus of levator ani muscle is ycT3NxM0 or below; The tumor below the hiatus of levator ani muscle is ycT2NxM0;
5. The patient underwent laparoscopic assisted TME surgery or robotic assisted TME surgery.

Exclusion Criteria:

1. multiple primary cancers;
2. history of open surgery;
3. no preoperative MR evaluation and inadequate evaluation of tumor stage;
4. Patients with rectal cancer who undergo endoscopic resection first and need subsequent transabdominal resection;
5. Pregnant or patients with concomitant inflammatory bowel disease;
6. Patients with preoperative complete bowel obstruction or requiring emergency surgery;
7. Preoperative evaluation indicates that patient may require combined organ resection;
8. Recently receiving treatment for other malignant tumors;
9. Bordeaux type IV low rectal cancer;
10. The preoperative pathological types are signet ring cell carcinoma, mucinous adenocarcinoma, undifferentiated carcinoma, or poorly differentiated carcinoma.

Exit Criteria

1. Refuse surgical treatment after randomization;
2. Open surgery was performed for treatment after randomization;
3. Patients request to withdraw from the study at any time during the entire study process after randomization