Neoadjuvant CAPOX With or Without Pucotenlimab Plus Selective Radiotherapy for Locally Advanced Rectal Cancer

This is a multicenter, phase III, randomized controlled trial. Eligible patients with pMMR/MSS locally advanced rectal cancer will be randomized in a 1:1 ratio to either the experimental group or the control group using stratified randomization, with mesorectal fascia (MRF) status as the stratification factor. Patients in the experimental group will receive four cycles of CAPOX plus pucotenlimab. Patients in the control group will receive four cycles of CAPOX alone. Tumor response will then be assessed. Patients with tumor shrinkage ≥20% and no persistent tumor involvement of the mesorectal fascia will proceed directly to surgery. Patients with tumor shrinkage \<20% or persistent MRF-positive disease will receive short-course radiotherapy, followed by two additional cycles of CAPOX plus pucotenlimab in the experimental group or CAPOX alone in the control group. After completion of neoadjuvant treatment, efficacy will be reassessed, and the timing of surgery will be determined according to treatment response. Postoperative adjuvant therapy will be decided by the investigator.