For high-risk stage II and stage III colorectal cancer, even after radical resection and postoperative adjuvant chemo/radiotherapy, 30-40% of patients will still have recurrence and metastasis. Thymosin-alpha 1 is believed to improve immunity and may help promote tumor immunity to reduce the incidence of recurrence and metastasis. This study hopes to verify the effecacy and safety of thymosin-alpha 1 for adjuvant treatment of high-risk stage II and stage III colorectal cancer after radical resection.

Patients with pathological high-risk stage II and stage III colorectal cancer after radical resection were randomly allocated to receive thymosin-alpha 1 twice a week for 6 months (experimental group) or not (control group) in a 1:1 ratio. At the same time, all patients will receive chemo/radiotherapy according to the Chinese Standards for Diagnosis and Treatment of Colorectal Cancer. The primary endpoint is 3-year DFS rate.

Inclusion Criteria:

• Colorectal cancer receiving radical resection
• Pathologically diagnosed with high-risk stage II or stage III
• Eastern Cooperative Oncology Group performance status of 0-2
• Adequate hepatic, renal, and hematologic function

Exclusion Criteria:

• Had previously taken any immune-promoting drugs
• Pregnancy or lactation

There is no masking for participants or investigators. The outcomes assessors will be blind for the allocation.