Chemotherapy (化疗) means chemotherapy, a treatment that kills tumor cells with cytotoxic drugs. In the past, chemotherapy, together with surgery and radiotherapy, was known as one of the three traditional treatments for cancer. Nowadays, with the rise of targeted therapy and immunotherapy, chemotherapy is not as important as it used to be, but it is still the cornerstone of tumor treatment. Chemotherapy is a systemic treatment mainly administered intravenously, but also by oral route, or by thoracic or abdominal perfusion. In some types of cancer, such as tumors of the germ cells, chemotherapy alone is often sufficient to achieve a cure. In many other malignant tumors that cannot be cured by chemotherapy, which have developed metastases in the middle and late stages, chemotherapy is still one of the main therapeutic means for treating cancer, which can greatly control the progression of the tumor and prolong the patient’s survival. Of course, chemotherapy will inevitably have some toxic side effects, so it must be administered by doctors specialized in oncology.