There are three main purposes for cancer patients to undergo chemotherapy in the first place. For some malignant tumors, patients can only undergo chemotherapy (e.g. hematological tumors), or certain tumors are sensitive to chemotherapy (e.g. choriocarcinomas), or patients are undergoing neoadjuvant therapy with a view to reducing the size of tumors. 1. Only chemotherapy can be administered: In some cancer patients, their primary tumors are already in advanced stages when they are diagnosed. At this time, the tumors have already metastasized to many parts of the body, and they have already lost the opportunity to have all the foci removed surgically (surgery will not have significant effect on their condition), and they often choose the comprehensive non-surgical treatments, including chemotherapy and radiotherapy, at this time. In addition, when non-solid tumors occur, such as hematological malignant tumors, they cannot be operated and can only receive chemotherapy. 2. Certain tumors are sensitive to chemotherapy, and the tumor can shrink or even disappear after chemotherapy, such as choriocarcinoma, which is clinically preferred to chemotherapy. 3. Some cancer patients, whose tumors are relatively huge and have the risk of not being able to be completely removed by one operation, but have not yet undergone systemic metastasis or only have local invasion, in order to be able to remove the tumors in one go, chemotherapy is often used to reduce the size of the tumors firstly, and then surgery can be carried out.