In this study, the investigators assessed the difference in efficacy and safety among robotic-assisted versus laparoscopic abdominoperineal resection for patients with low rectal cancer.

Patients will be eligible for inclusion if their primary tumors is low rectal cancer.

Eligible patients will be randomly assigned to robotic-assisted (arm A) versus laparoscopic (arm B) abdominoperineal resection.

Inclusion Criteria:

• Histologically proven rectal adenocarcinoma
• Inferior edge of the tumor located within 5 cm from the anal verge as determined by colonoscopy withdrawing and digital rectal examination
• No evidence of distant metastases (including pelvis, peritoneum, liver, lung, brain, bone, distant lymph node, etc) according to ultrasound, CT, PET-CT, etc
• Tumor assessed as cT1-T3 or ycT1-T3 after preoperative neoadjuvant chemoradiotherapy by pelvic MRI
• No other malignancies in medical history except adequately treated basocellular carcinoma of the skin or in situ carcinoma of the cervix uteri
• Suitable for both robot-assisted and laparoscopic surgery
• American Society of Anesthesiologists (ASA) class I - III
• No other preoperative treatment except neoadjuvant chemoradiotherapy
• Informed consent

Exclusion Criteria:

• Tumors assessed as cT1N0 and suitable for local excision
• Signs of acute intestinal obstruction, bleeding or perforation needing emergency surgery
• More than one colorectal tumor
• Familial Adenomatosis Polyposis, Lynch Syndrome, acute inflammatory bowel disease
• Schedules need for other synchronous colon surgery
• Absolute contraindications to general anesthesia or prolonged pneumoperitoneum (ASA class > III)
• Pregnancy or lactation
• Patients and/or family members can not understand and accept this study
• Patients received chemoradiotherapy or other anti-tumor therapy before surgery