Radiation therapy, or radiotherapy for short, is a means of treating disease with radiation. It is mainly used to treat malignant tumors, but can also treat some benign diseases. In the treatment of cancer patients, about 70% of patients need to use radiotherapy; according to the World Health Organization, about 18% of tumors can be cured radically with radiotherapy. Radiation therapy is a specialized discipline called radiation oncology. The role of radiotherapy and its status in tumor treatment Radiotherapy is a local treatment, which can be used to destroy and cure local primary tumors or metastatic lesions. Some early stage tumors have high cure rate by radiotherapy alone, such as early stage esophageal cancer, cervical cancer, vocal cord cancer, Hodgkin’s lymphoma, skin cancer and so on. The 5-year survival rate of early esophageal cancer, prostate cancer, tongue cancer, etc. are similar to that of surgery, and the cosmetic effect is more satisfactory. Besides simple radiotherapy, radiotherapy also plays an important role in the comprehensive treatment of tumors, especially for some patients in the middle and late stages, through preoperative, intraoperative and postoperative radiotherapy with surgery; radiotherapy before, during and after chemotherapy with chemotherapy; as well as the comprehensive treatment with radiotherapy, surgery and chemotherapy, so that the cure rate of malignant tumors can be significantly increased. In conclusion, radiotherapy is an important treatment for most of the malignant tumor patients. The advantages of radiotherapy are: 1. Its advantages are: 1. It does not require high requirements for patients to receive treatment: many patients who are old, poor in health, or have undergone many previous operations can still receive radiotherapy; 2. The side effects of treatment are relatively small and can avoid anesthesia accidents caused by surgery, blood transfusion reaction, postoperative infection or side effects such as hair loss and vomiting caused by chemotherapy; 5. It is non-invasive treatment, and simple radical radiotherapy for early tumors can preserve the physiological functions of organs while eliminating tumors; 6. Preoperative radiotherapy can improve the resection rate of surgery without affecting the improve the rate of organ preservation; postoperative radiotherapy can reduce the local recurrence rate and improve the survival rate. The time required for a course of radiotherapy depends on the nature of the tumor, the early and late lesions, the purpose of treatment, the patient’s physical condition and other factors, and generally takes 4~6 weeks. For tumors with relatively early lesions and located in parenchymal organs, such as lung cancer and liver cancer, radical radiotherapy with stereotactic radiotherapy as the main treatment takes less time, generally 2~3 weeks; for nasopharyngeal cancer and esophageal cancer, radical radiotherapy generally takes 6~7 weeks; for palliative radiotherapy with more advanced lesions, it takes 3~5 weeks, such as radiotherapy for multiple metastases in the brain, it generally takes 2~4 weeks. Radiotherapy for sensitive tumors generally takes less time, e.g., 3.5-5.5 weeks for lymphoma, and 6-8 weeks for less sensitive tumors, e.g., fibrosarcoma. Pre-operative radiotherapy to improve surgical resection rate and reduce recurrence usually takes 4-5 weeks; post-operative radiotherapy to consolidate the efficacy usually takes 5-6 weeks, for example, 5 weeks for rectal cancer.