Radiation therapy is the abbreviation of radiation therapy, commonly known as “baking electricity”, “light”, “electrotherapy”, which is the use of alpha, beta, gamma radiation produced by radioisotopes and different energy radiation produced by X-ray therapy machines and various accelerators to treat malignant tumors. It is a science of treating malignant tumors by using α, β, γ radiation produced by radioisotopes and different energy radiation produced by X-ray therapy machines and various gas pedals, such as electron rays, proton rays, neutron rays, negative π meson rays and other heavy particle rays. The mechanism is: radiation entering the human body can produce secondary electrons, causing ionization effect and damaging the DNA of biological macromolecules in the nucleus of tumor cells, resulting in the death of tumor cells. Radiation therapy is mainly carried out by taking advantage of the difference in the killing and repair ability of radiation to normal tissue cells and tumor cells, and maximizing the killing of tumor cells under the conditions that normal tissue cells can tolerate. Its characteristic is: it has a great effect on infantile and vigorous growth tumor cells; the disadvantage is: while radiation destroys and kills tumor cells, it also has a destructive effect on surrounding normal tissue cells. In recent years, due to the improvement of radiotherapy equipment and the development of radiation physics, radiobiology, oncology and other disciplines, the position of radiotherapy in tumor treatment is becoming more and more important, according to statistics, about 60-70% of malignant tumor patients, in different periods of the course of the disease due to different needs and According to statistics, about 60-70% of malignant tumor patients can receive radiation therapy at different times of the disease process, and about 70% of the patients who receive radiation therapy can implement radical radiotherapy, and radiation therapy can cure tumor has been fully affirmed. Radical radiotherapy: It is to give radical dose to make the tumor treatment obtain satisfactory efficacy. Its indications are tumors with early disease, tumor pathology type sensitive or moderately sensitive to radiation, and patients with good general condition can tolerate radical dose irradiation, such as nasopharyngeal cancer, laryngeal cancer, tonsil cancer, cervical cancer, nasal cavity cancer, pituitary tumor, malignant lymphoma, medulloblastoma, Ewing’s sarcoma, seminoma, lung cancer, brain pineal tumor, etc. 2.Palliative radiotherapy: For patients with late stage of disease and poor general condition, radiotherapy can achieve the purpose of relieving symptoms, alleviating pain and improving quality of life. It is often used to relieve tumor compression and obstruction, stop bleeding and pain, such as esophageal obstruction, superior vena cava compression, spinal cord compression, etc. For bone metastases, especially for osteolytic bone destruction caused by breast cancer and lung cancer, radiation pain relief is more effective. About 80% to 90% of patients can get different degrees of pain relief after 1 to 2 weeks of radiation therapy, and 50% of patients can achieve complete relief. When can’t radiotherapy be given to patients with advanced cancer, such as those who are obviously malignant, dehydrated and in very poor nutritional condition; esophageal cancer with perforation and large amount of fluid in the cavity; lung cancer with large amount of pleural fluid; liver cancer with large amount of ascites; tumors with low sensitivity to radiation; those who have been treated with local radiotherapy but have relapsed and normal tissues no longer tolerate the second radiotherapy. In addition, patients with other serious diseases, such as acute infection, heart failure, heart disease and tumor located near the heart (such as lung cancer); lung cancer patients with severe lung function insufficiency, etc., are not suitable for radiotherapy. V. What are the adverse reactions of radiotherapy? The adverse local reactions of radiotherapy mainly refer to local dry skin dermatitis and wet dermatitis, which can form radioactive fibrosis later. Such as irradiation of oral cavity can cause decrease of salivary gland function and dry mouth; such as irradiation of bladder and rectum can cause radioactive cystitis (more frequent urination, painful urination, hematuria) and radioactive proctitis (more frequent stool, cramping, red and white pepto); such as excessive brain irradiation can cause brain necrosis and excessive spinal cord irradiation can cause paraplegia. Generally speaking, there is no need to suspend radiotherapy, as long as we carry out radiotherapy reasonably, there will be no serious local and systemic reactions.