Neoadjuvant Short-Course Radiotherapy Followed by CAPOX Plus PD-1 Antibody and IL-2 in Locally Advanced Rectal Cancer

Inclusion Criteria: * Males and females aged between 18 and 70 years; * ECOG (Eastern Cooperative Oncology Group) performance status score of 0 or 1; * Tumor tissue samples obtained and histologically confirmed as rectal adenocarcinoma; * Adequate hematological, liver, and kidney functions: neutrophil count ≥ 1.5×10\^9/L; platelet count ≥ 75×10\^9/L; serum total bilirubin ≤ 1.5× upper limit of normal (UNL); aspartate aminotransferase ≤ 2.5× UNL; alanine aminotransferase ≤ 2.5× UNL; serum creatinine ≤ 1.5× UNL. Exclusion Criteria: * Metastatic disease (Stage IV); * Recurrent rectal cancer; * Concurrent active bleeding, perforation, or other complex situations that cannot be addressed with emergency colostomy surgery alone; * Previous systemic anti-cancer treatment for colorectal cancer; * Coexistence of other non-colorectal cancer malignancies; * Patients with any active autoimmune diseases, or a history of needing steroids or immunosuppressive drugs; * Patients with interstitial lung disease, non-infectious pneumonia, or uncontrolled systemic diseases (e.g., diabetes, hypertension, pulmonary fibrosis, and acute pneumonia); * Previous treatment-induced any grade 2 or above toxicity reaction (according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5 classification) that has not subsided (excluding anemia, hair loss, and skin pigmentation); * Previous treatment with anti-programmed death receptor-1 (PD-1) or its ligand (PD-L1) antibodies, anti-cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) antibodies; * Pregnant or breastfeeding women; * Known or tested positive for human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS); * Known or suspected allergy history to any drugs used in the trial.