This study aims to evaluate the efficacy (pathological complete response rate) of short-course radiotherapy with preservation of tumor-draining lymph nodes followed by sequential PD-1 inhibitor neoadjuvant therapy in patients with stage II-III pMMR/MSS locally advanced rectal cancer.
Age 18-75 years old, regardless of sex.
Fibrocolonoscopy or digital rectal examination indicates that the distal border of the lesion is located 5-10 cm from the anal verge.
Pathologically confirmed rectal adenocarcinoma.
Imaging examinations (including pelvic MRI and chest-abdominal CT) confirm a clinical stage of II/III (cT3-T4aN0 or cT2-4aN+, MRF (-), with no distant metastasis) according to the AJCC Cancer Staging Manual, 8th Edition (2018) (for detailed TNM staging of rectal cancer).
Previous treatment with anti-PD-1/L1, anti-CTLA-4 immunotherapies, or other investigational immunotherapeutic agents is excluded.
Patients with severe autoimmune diseases are excluded, including active inflammatory bowel disease (such as Crohn's disease, ulcerative colitis), rheumatoid arthritis, scleroderma, systemic lupus erythematosus, autoimmune vasculitis (e.g., Wegener's granulomatosis), etc.
Patients with symptomatic interstitial lung disease or active infectious/non-infectious pneumonitis are excluded.
Patients with clinical or imaging evidence of intestinal obstruction or perforation, or those deemed by the investigator to be at high risk of perforation or hemorrhage, are excluded.