Chemoradiotherapy After Surgery Versus Preoperative Chemoradiotherapy for Stage II/III Mid-low Rectal Cancer With or Without High-risk Factors

Inclusion Criteria: 1. The patient is between 18 and 80 years old; 2. Adenocarcinoma confirmed by pathology; 3. Colonoscopy or imaging examination confirmed that the distance between the lower edge of the tumor and the anal margin is ≤10cm; 4. ECOG score ≤2 (4) Imaging diagnostic analysis was cT1-3NxM0; (for Phase II/III) (5) CT examination of the chest and abdomen and pelvis showed no evidence of metastasis (6) Patients undergoing chemoradiotherapy and surgery Exclusion Criteria: 1. History of malignant tumors in the past; 2. Diagnosis of simultaneous multiple primary colorectal cancer or other cancers; 3. History of chemotherapy or radiotherapy prior to this trial 4. Those with contraindications to laparoscopic surgery, such as severe cardiopulmonary insufficiency; 5. Patients with intestinal obstruction, intestinal perforation, intestinal bleeding, etc., requiring emergency surgery; 6. Pregnant or lactating women; 7. Evidence of distant metastases prior to surgery 8. T4b tumors were found to invade the uterus, vagina, bladder, seminal vesicles, prostate, bone, and pelvic plexus