SCRT Combined With CAPOX and PD-1/CTLA4 Antibody for Early-stage Low Rectal Cancer

The study evaluates the combination of immunotherapy of PD-1/ CTLA4 antibody and neoadjuvant short-course radiotherapy in early low rectal cancer. A total of 34 patients will receive 5\*5Gy short-course radiotherapy, followed by 4 cycles of capecitabine plus oxaliplatin (CAPOX) chemotherapy and PD-1/ CTLA4 antibody, finally receive the local excision(TEM) or total mesorectal excision (TME). The rate of complete response (cCR+pCR), Organ retention rate, long-term prognosis, and adverse effects will be analyzed.

Inclusion Criteria: 1. age 18-75 years old, female and male 2. pathological confirmed adenocarcinoma 3. clinical stage T1-3bN0, tumor maximum diameter less than 4cm 4. the distance from anal verge less than 5 cm 5. without distance metastases 6. KPS \>=70 7. with good compliance 8. microsatellite repair status is MSS/pMMR 9. without previous anti-cancer therapy or immunotherapy 10. signed the inform consent Exclusion Criteria: 1. pregnancy or breast-feeding women 2. pathological confirmed signet ring cell carcinoma 3. clinical stage T1N0 and can be resected locally 4. history of other malignancies within 5 years 5. serious medical illness, such as severe mental disorders, cardiac disease, uncontrolled infection, etc. 6. immunodeficiency disease or long-term using of immunosuppressive agents 7. baseline blood and biochemical indicators do not meet the following criteria: neutrophils≥1.5×10\^9/L, Hb≥90g/L, PLT≥100×10\^9/L, ALT/AST ≤2.5 ULN, Cr≤ 1 ULN 8. DPD deficiency 9. allergic to any component of the therapy