Radiotherapy is one of the three main treatments for malignant tumors and is a local area treatment that can be used to eradicate or relieve localized primary tumors or metastases. Radiotherapy can be applied alone or in combination with surgery and chemotherapy to treat tumors. Radiotherapy is required for about 50-70% of cancer patients during the consultation and treatment process. According to the World Health Organization, 45% of tumors can be cured, of which about 18% of malignant tumors can be cured radically by radiotherapy, 22% by surgery and 5% by chemotherapy. 1.Radical radiotherapy Definition: It refers to radiation therapy as the main treatment or radiotherapy alone can achieve the purpose of curing tumor. Applicable diseases: Nasopharyngeal cancer, laryngeal cancer, head and neck tumor, cervical cancer, Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, prostate cancer, skin cancer, anal canal cancer, medulloblastoma, Langerhans’ tissue hyperplasia, etc. The 5-year survival rate of radiation therapy for early esophageal cancer, tongue cancer and prostate cancer is the same as that of surgery, and the functional preservation and cosmetic effects are better. For tumors that can be cured radically through surgery, if patients are contraindicated to surgery or unwilling to have surgery, radiotherapy is usually the best alternative, and many patients can be cured after treatment. 2.Radiotherapy is the main treatment: such as stage III non-small cell lung cancer, locally advanced pancreatic cancer, etc. In recent years, the use of conformal radiotherapy or intensity-modulated radiotherapy for inoperable non-small cell lung cancer, liver cancer, pancreatic cancer, etc. has not only improved the efficacy but also significantly reduced the side effects of treatment, opening up a new treatment pathway for many inoperable tumors. 3.Comprehensive treatment (adjuvant treatment): radiation therapy also has a very important position in the comprehensive treatment of tumors. (1) Pre-operative radiotherapy or radiochemotherapy: it can shrink the tumor, allowing some patients to regain the opportunity of surgery or radical resection to improve the efficacy, or reduce the scope of surgical resection and preserve the function of organs, such as locally advanced head and neck cancer, breast cancer, rectal cancer, esophageal cancer, etc. (2) Postoperative radiotherapy or radiochemotherapy: it can effectively kill the residual tumor or subclinical lesions after surgery, and is suitable for the postoperative treatment of most of the middle and late stage tumors, such as brain tumor, head and neck cancer, esophageal cancer, non-small cell lung cancer, rectal cancer, soft tissue sarcoma, etc. The efficacy of local excision of early breast cancer tumor plus postoperative radiotherapy is the same as that of total mastectomy, but it preserves the breast and has good cosmetic effect and improves the The quality of life of patients is improved. 4. Palliative radiotherapy: It is mainly aimed at relieving or preventing patients’ clinical symptoms and improving their quality of life, and sometimes it can significantly prolong patients’ survival, which is mainly applied to radiotherapy for advanced tumors, such as brain metastases, bone metastases and superior vena cava compression syndrome. All in all, radiotherapy is an indispensable and effective treatment for most malignant tumor patients. Patients should go to radiotherapy department in time to determine the best treatment plan and strive for the best curative effect.