Inclusion Criteria:

1. Male or female patients ≥ 18 years of age;

2. CRC with histological diagnose, and had received neoadjuvant and (or) adjuvant
chemotherapy or (and) radiotherapy and got complete response (CR) with imaging;

3. Patients who have a life expectancy of at least 3 months;

4. Eastern Cooperative Oncology Group (ECOG) performance status was 0 - 1;

5. The bone marrow functioned normally (WBC > 4.0×109/L, Hb > 120 g/L, PLT > 100×109/L);

6. The ECG results were normal, and the liver and kidney were functional.

Exclusion Criteria:

1. Patients who had distant metastases;

2. Patients with uncontrolled infection; underlying disease that was severe or
life-threatening;

3. Patients who were pregnant or lactating;

4. ECOG perform status ≥ 2;

5. Patients who are suffering from auto immune diseases or patients who need to accept
glucocorticoid treatment.