Application of PD-1 Monoclonal Antibody in Combination With IL-2 and CapeOX in Organ Preservation Therapy for Ultra-Low Localized Advanced Rectal Cancer

Inclusion Criteria:

1. Age ≥18 years and ≤75 years
2. Histologically confirmed adenocarcinoma of the rectum
3. pMMR (proficient mismatch repair) or MSI-L (microsatellite instability-low) or MSS (microsatellite stable)
4. Tumor distance from the anal verge ≤5 cm
5. Clinical stage of cT1-3N1M0 or cT2-3N0M0
6. ECOG performance status score ≤ 1

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.