Neoadjuvant Short-Course Radiotherapy With or Without Chemotherapy and AK112 in Locally Advanced Rectal Cancer

Inclusion Criteria: 1. Signed written informed consent. 2. Age 18-80 years, male or female. 3. Histologically confirmed rectal adenocarcinoma. 4. Clinical baseline stage T3-4NxM0 or TxN1-2M0 by MRI assessment. 5. Able to swallow tablets. 6. ECOG Performance Status of 0-1. 7. No prior treatment for rectal cancer, including surgery, radiotherapy, 8.chemotherapy, immunotherapy, or targeted therapy. 9.Fit for surgery with no contraindications. 10.Normal organ function. 11.Tumor ≤12 cm from the anal verge Exclusion Criteria: 1. Allergy to monoclonal antibodies, AK112 components, or CapeOX regimen. 2. Previous or current use of immune checkpoint inhibitors or immune-related 3.treatments. 4.Active autoimmune diseases or history of significant autoimmune conditions. 5.Immunodeficiency disorders or history of organ/bone marrow transplantation. 6.Uncontrolled cardiovascular conditions (e.g., heart failure, unstable angina, recent MI). 7.Severe infection within 4 weeks or active pulmonary infections. 8.Active hepatitis B or C infection. 9.Diagnosis of other malignancies within 5 years (except low-risk cancers). 10.Pregnant or breastfeeding women.