Assessment of Efficacy and Safety of PD-1 Monoclonal Antibody Combined With IL-2 and CapeOX in Neoadjuvant Therapy for Locally Advanced Rectal Cancer Prior to Surgery: A Prospective, Multi-center, Randomized Controlled Study

The objective is to evaluate whether the neoadjuvant combination of tislelizumab (a PD-1 inhibitor) with interleukin-2 (IL-2) chemotherapy can significantly increase the Objective Response Rate (ORR) and the Pathological Complete Response rate (pCR) in patients with locally advanced rectal cancer who have Microsatellite Stable/Proficient Mismatch Repair (MSS/pMMR) status.

Inclusion Criteria: 1. Males and females aged between 18 and 75 years; 2. An Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1; 3. Histologically confirmed rectal adenocarcinoma; 4. Clinical stage T3-T4 or any T with node-positive (N+) disease: locally advanced; 5. Microsatellite stable (MSS) status; 6. Adequate hematological, hepatic, and renal functions. Exclusion Criteria: 1. Patients with metastatic disease (Stage IV); recurrent colorectal cancer with active bleeding, perforation, or complex conditions requiring urgent surgery; or concurrent non-colorectal cancer malignancies. 2. Patients who have previously received systemic anticancer therapy for colorectal cancer; or have been treated with PD-1, PD-L1, or CTLA-4 antibodies. 3. Patients with any active autoimmune disease; known or tested positive for Human Immunodeficiency Virus (HIV) or Acquired Immunodeficiency Syndrome (AIDS); or a history requiring steroid or immunosuppressive drug treatment. 4. Patients with interstitial lung disease, non-infectious pneumonitis, or uncontrolled systemic diseases (such as diabetes, hypertension, pulmonary fibrosis, and acute pneumonia). 5. Patients who experienced any Grade 2 or higher toxicities due to prior treatments (as classified by the Common Terminology Criteria for Adverse Events \[CTCAE\] version 5), which have not resolved (excluding anemia, alopecia, and skin pigmentation changes); known or suspected history of hypersensitivity to any of the drugs used in the trial. 6. Pregnant or breastfeeding women.