Cancer may recur after removal. Although all visible cancer has been removed through surgery, it cannot be ruled out that there are still tiny foci around the cancer that cannot be seen by the naked eye, or that the cancer cells have already metastasized to other parts of the body through blood or lymph, only that these foci are relatively small, and they cannot be shown through the current CT, ultrasound, MRI and other examinations. After a period of time, with the growth of tumor cells, recurrence or distant metastasis of the tumor will be found through review. Therefore, many postoperative cancer patients also need to undergo adjuvant radiotherapy and chemotherapy according to the pathology to reduce the chances of local recurrence and distant metastasis, so as to improve the cure rate of cancer.