Overview

The study evaluates the combination of immunotherapy of PD-1 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 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.

Eligibility

Inclusion Criteria:

1. age 18-70 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