Overview

TORCH-E2 is a prospective, multicentre, randomized phase II trial. 134 low-lying early (T1-3b/N0-1M0, distance from anal verge ≤5cm) patients will be recruited and assigned to Group 1 and Group 2 (1:1). Group 1 receives SCRT (25Gy/5Fx) followed by 4 cycles of capecitabine plus oxaliplatin (CAPOX) chemotherapy and PD-1 antibody. Group 2 receives LCRT (50Gy/25Fx) followed by 2 cycles of CAPOX. A WW option can be applied to patients achieving cCR while surgery will be recommended for those who fail to achieve cCR. The primary endpoint is complete response (CR, pathological complete response [pCR] plus cCR) rate. The secondary endpoints include the grade 3-4 acute adverse effects (AE) rate, anal preservation rate, 3-year DFS rate, etc.

Eligibility

Inclusion Criteria:

1. age 18-75 years old, female and male
2. pathological confirmed adenocarcinoma
3. clinical stage T1-3bN0-1, 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