Robotic Versus Laparoscopic Surgery for Middle and Low Rectal Cancer: a Target Trial Emulation

Inclusion criteria: 1. Age from 18 years to 80 years; 2. American Society of Anesthesiologists (ASA) class I - III; 3. Histologically proved rectal adenocarcinoma; 4. Inferior tumor edge ≤ 10 cm from anal verge, measured by rigid rectoscopy; 5. Tumor assessed as cT1-T3 (mesorectal fascia not involved) N0-1, or ycT1-T3 Nx after preoperative radio- or chemoradiotherapy, measured by pelvic MRI; 6. No evidence of distant metastases (including pelvis, peritoneum, liver, lung, brain, bone, distant lymph node, etc), according to ultrasound, CT, MRI, PET-CT, etc; 7. No other malignancies in medical history except adequately treated basocellular carcinoma of the skin or in situ carcinoma of the cervix uteri; 8. Received either robotic or laparoscopic surgery; 9） Surgery with radical intent; 10\) Informed consent. Exclusion criteria 1. Emergency surgery for acute intestinal obstruction, bleeding, perforation, etc; 2. Synchronous colon surgery for multiple colorectal tumors or other schedules; 3. Hereditary colorectal cancer (familial adenomatosis polyposis, Lynch Syndrome, etc.); 4. Co-existent inflammatory bowel disease; 5. Pregnancy or lactation; 6. Patients received treatment other than preoperative radio- or chemoradiotherapy.