Table 2 Inclusion, exclusion, and withdrawal criteria

• 18 years < age < 85 years

• Pathological colorectal adenocarcinoma

• Tumor located in colon and rectum (the lower border of the tumor is above the peritoneal reflection)

• Clinically diagnosed cT1-4aN0-2M0 lesions according to the 8th Edition of AJCC Cancer Staging Manual without preoperative neoadjuvant therapy performed

• Tumor size of ≤ 5 cm

• Performance status ECOG 0–1

• ASA class I to III

• Informed consent

• BMI > 35 kg/m2

• Previous gastrointestinal surgery (except for appendicectomy)

• Emergency operation due to complication caused by colorectal cancer (bleeding, perforation or obstruction)

• Multiple malignant lesions

• Familial adenomatous polyposis (FAP) or Inflammatory bowel disease (IBD)

• Requirement of neoadjuvant therapy

• Pregnancy or lactation

• Severe mental disease

• Severe liver and kidney dysfunction, coagulation dysfunction, or with serious comorbidities that cannot perform surgery

• Requirement of simultaneous surgery for other disease

• Other malignant disease history within 5 years

• Intraoperative or pathological confirmation of invasion of adjacent structures requiring combined organ resection or distant metastasis

• Non-colorectal adenocarcinoma confirmed by postoperative pathology

• Multiple malignant lesions confirmed by postoperative pathology

• Requirement of emergency operation due to the change of illness state

• Inability to undergo surgery or anesthesia due to the change of illness state

• Receive treatment other than the protocol during the treatment period (except for treatment of tumor recurrence and metastasis)

• Patient required to withdraw

• Unable to complete the clinical trial due to various reasons

• Treatment implemented is proven to violate the study protocol