This study aims to compare the effectiveness of robotic surgery versus laparoscopic surgery in treating low rectal cancer. While robotic surgery has gained popularity, there is limited long-term evidence regarding its outcomes. By using real-world data from a specialized multicenter colorectal cancer database in Shanghai, China, this retrospective cohort study will emulate the target trial to evaluate whether robotic surgery offers advantages over laparoscopic surgery. Key factors such as disease-free survival, locoregional recurrence, circumferential margin positivity, and postoperative complications will be examined. The goal is to provide stronger, evidence-based support for the clinical use of robotic surgery in treating low rectal cancer.

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.

The data is sourced from the Colorectal Cancer Specialty Cohort Database and Biobank, established through the "Construction and Application of the Shanghai Colorectal Cancer Specialty Cohort Database and Biobank" project. The research will utilize cohort data collected from January 2021 to May 2022 (17 months). This specialized database was led by Zhongshan Hospital, Fudan University, in collaboration with Shanghai Tenth People's Hospital, Fudan University Shanghai Cancer Center, First Affiliated Hospital of Naval Medical University (Changhai Hospital), Renji Hospital, Shanghai Jiao Tong University School of Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, and Shanghai First People's Hospital.