Radiation therapy can treat cancer and can be curative for some cancers, such as lymphoma and nasopharyngeal carcinoma. Radiotherapy can also shrink tumors, which can greatly help to reduce the risk of surgery and improve the quality of survival of cancer patients. However, the electromagnetic radiation produced by radiotherapy can kill cancer cells, but also have adverse effects on normal cells, causing local damage or systemic reactions: 1. local damage: 1. brain damage: large exposure to electromagnetic radiation in the brain can lead to brain atrophy, brain edema, brain necrosis, etc., and may also cause spinal cord injury resulting in paraplegia; 2. respiratory damage: coughing, shortness of breath and even lung inflammation can occur after radiotherapy. Radiotherapy patients can also cause lung fibrosis and gradually lose the function of ventilation; 3, gastrointestinal tract injury: inflammatory lesions can be produced in the gastrointestinal tract, with abdominal pain and diarrhea in mild cases, and ulcers, perforation and local intestinal necrosis in severe cases, etc. Radiotherapy to the liver can cause liver function damage or even liver failure; 4, other: radiotherapy local skin can cause skin burns, skin breakdown is easy to secondary infection, and can even lead to subcutaneous tissue fibrosis, stiffness of limb joints. Systemic reactions: Besides local radiation damage, radiotherapy can also affect the whole body, such as fatigue, nausea and vomiting, loss of appetite, reduced white blood cells, unresponsiveness and insomnia after radiotherapy. Meanwhile, inflammatory foci of radiotherapy may cause ascites and pelvic effusion, and long-term high-dose radiotherapy may also lead to sterility. In addition, long-term radiotherapy may induce genetic mutations, which may cause the body to produce new tumors.