Radiation therapy for lung cancer (radiotherapy for short) uses high-energy rays to kill cancer cells and is a local treatment that only kills tumor cells in the irradiated area. Radiation therapy for lung cancer often uses external radiation (a treatment machine at a certain distance from the body emits radiation into the body for treatment). Brachytherapy is also used: radiation sources are placed directly or through the trachea or bronchus into the tumor area for treatment. Under what circumstances is radiotherapy needed? 1. Early stage lung cancer patients who have contraindications to surgery or refuse surgery can undergo radical radiotherapy. Studies have shown that the effect of 3D conformal intensity modulated radiotherapy for early stage lung cancer is comparable to the long-term survival rate of radical surgery. 2.Stage III non-small cell lung cancer is the main indication for radiotherapy. It is estimated that if there is difficulty in surgical resection, especially when CT shows involvement of large blood vessels and other important tissues and organs, preoperative radiotherapy can be given; if there is residual or regional lymph node metastasis after surgery, markings should be made and postoperative radiotherapy should be given. 3. For advanced lung cancer with extensive lesions and serious symptoms, such as combined brain metastasis, bone metastasis, superior vena cava compression, etc., palliative radiotherapy can be done to improve symptoms and life quality. 4. Radiotherapy for small cell lung cancer on the primary foci and lymphatic drainage area on the basis of chemotherapy can increase the local control rate and prolong the remission period. Preventive irradiation to the brain can reduce the rate of brain metastasis. What should be noted in radiotherapy? 1.Avoid smoking, because smoking will aggravate the side effects of radiotherapy in the respiratory tract; 2.Avoid cold infection, because lung infection will aggravate the radiation pneumonia in the lungs; 3.Be sure to insist on doing the whole course of treatment (the dose of radiotherapy should be sufficient) and avoid giving up halfway; 4.Once the radiation pneumonia appears, especially the outpatient radiotherapy patients must see the doctor as soon as possible to give treatment; 5.Be sure to check the blood routine every week during the radiotherapy process Check the blood routine every week during radiotherapy, observe the changes of white blood cells and deal with them in time; 6. Pay attention to strengthen nutrition and ensure sleep during treatment; 7. Immune booster can be given during radiotherapy to regulate the immune function of patients when available.