Radiotherapy, whose big name is radiation therapy, is a treatment by a brilliant physicist who is able to use various types of rays of different energies against tumors in order to inhibit and kill tumor cells. His weapons are machines that can produce various types of rays, commonly electron linear gas pedals. Chemotherapy, on the other hand, is the brilliant chemopharmacologist, specializing in the application of chemical drugs (including endocrine drugs, etc.) to fight against tumors. It is commonly used intravenously, orally or in other forms to let chemotherapeutic drugs enter the body to kill tumors. The scope of radiation therapy is called “target area”, that is, the area where the radiation is concentrated, but outside the target area, there are not many rays and normal tissues will not be damaged. After determining the size of the tumor and its invasion site based on imaging and other clinical examinations, radiotherapists must understand the biological characteristics of the tumor and the rule of spread before deciding the radiation scope. Chemotherapy is a systemic treatment, and the drugs will be distributed to all parts of the body after entering the body, which will not only have an effect on solid tumors, but also have a strong killing effect on small invisible metastases. Of course, there are also local treatment-based chemotherapy such as interventional chemotherapy, local infusion chemotherapy and so on. 2.The objects they attack are different Radiation therapy mainly aims at the radical treatment of relatively limited solid tumors, such as head and neck tumors, lung cancer, esophageal cancer, skin cancer, lymphoma, etc.; preoperative and postoperative adjuvant treatment of some tumors, such as breast cancer, cervical cancer, gastrointestinal tumors; some other tumors, such as bone and brain metastases, palliative radiotherapy, etc., while for systemic tumors, such as leukemia, the effect is limited. At present, about 70% of tumor patients need to receive radiotherapy at different stages of the disease process, which shows the importance of radiotherapy in tumor treatment. Chemotherapy is used for tumors that are sensitive to chemotherapy drugs, such as lymphoma, leukemia and other hematologic diseases, breast cancer, gastrointestinal tumors, lung cancer, reproductive tumors and so on. The effect of chemotherapy depends on the type and condition of the tumor, some of which can be cured and more often inhibit the growth and spread of the tumor. With the emergence of new technologies, the indications for radiotherapy are changing. 3.Toxic side effects are different. In general, radiotherapy is mainly local reaction, which is related to radiotherapy field. For example, head and neck radiotherapy may cause dry mouth, sore throat, neck fibrosis, loss of taste function, etc. Radiotherapy to the chest may result in radioactive lung changes, radioactive esophagitis, etc. With the advancement of radiotherapy technology, radioactive brain damage and paraplegia, which used to occur frequently, are less common. The main reactions to chemotherapy are systemic reactions, usually bone marrow suppression, gastrointestinal reactions, such as decreased blood count, nausea, vomiting, and phlebitis. With proper management, serious liver and kidney damage, cardiac damage, and severe reactions such as “vomiting out the bile” are not very common in clinical practice. Nowadays, technology is developing, and the toxic side effects of radiotherapy are gradually being reduced. Although radiotherapy and chemotherapy are so different, in fact, radiotherapy, chemotherapy and surgery are used in conjunction with each other in the treatment of many tumors. Breast cancer and lung cancer are the most common cases of comprehensive treatment. As for when a tumor should be operated, when it should be treated with radiotherapy, when it should be treated with chemotherapy, and when it should be treated with palliative care, it depends on the clinicians, imaging physicians, pathologists and related medical personnel to make a decision through a comprehensive judgment of the patient’s disease stage, physical condition and other general conditions.