The number of cancer cells that can be killed by chemotherapy at one time is not certain, as it is related to the type of cancer and the sensitivity of the cancer cells to chemotherapy. Chemotherapy is mainly used in the treatment of malignant tumors to kill cancer cells and inhibit their growth. For cancers with high sensitivity to chemotherapy, such as choriocarcinoma and malignant lymphoma, the percentage of cancer cells that can be killed by chemotherapy at one time is relatively high, and there is even a possibility of cure. If the cancer is not sensitive to chemotherapy, such as liver cancer and pancreatic cancer, the number of cancer cells killed by chemotherapy at one time is very small. Generally, a course of chemotherapy is 4-8 times. Chemotherapy once cannot maintain a long-lasting therapeutic effect, nor can it kill the cancer cells completely, and it has to be continued in order to inhibit the growth of cancer cells effectively. Moreover, it takes more than one course of chemotherapy to kill more cancer cells in the body, slow down the process of cancer deterioration, and reduce the possibility of metastasis and recurrence of cancer cells.