Surgery is preferred for colorectal cancer without distant metastases, and postoperative adjuvant chemotherapy is often required to kill any tumor cells that may remain in the body. However, not all colorectal cancer patients can benefit from postoperative adjuvant chemotherapy. Which patients need post-operative adjuvant chemotherapy? The oncology guidelines developed by the National Comprehensive Cancer Network are internationally recognized as the definitive guidelines in the field of oncology. The guidelines recommend that postoperative adjuvant chemotherapy is required if one of the following conditions is present: 1. postoperative pathologic T-stage of colon cancer is T4; postoperative pathologic T-stage of rectal cancer is T3 or T4; 2. postoperative pathologic stage III, i.e., with lymph node metastasis; 3. tumor grade 3-4; 4. with vascular cancer embolus; 5. preoperative with intestinal obstruction; 6. preoperative with tumor perforation; 7. positive incisional margin or The condition of cutting edge is uncertain; 8. Pathologically detected lymph nodes <12. Postoperative adjuvant chemotherapy is not recommended if the tumor is at an early pathological stage and there are no high-risk factors mentioned above.