As a common saying goes, “medicine is poisonous in three parts”. It means that in addition to its therapeutic effects, drugs usually have more or less adverse effects on people outside of treatment. The common side effects include systemic and localized ones. Before radiotherapy, doctors usually communicate well with patients to let them fully understand the necessity of radiotherapy and the possible side effects of radiotherapy. This can eliminate the patient’s anxiety and allow the patient to work together with the doctor to take targeted measures and carefully understand the relevant precautions, which can considerably reduce the side effects of radiotherapy and alleviate the patient’s pain. Systemic side effects: They usually refer to patients’ loss of appetite, fatigue, dizziness, headache, insomnia and immune deficiency during and after radiotherapy, etc. In addition, some patients may have gastrointestinal reactions such as nausea and vomiting, indigestion and gastric distension, etc. The situation is usually not very serious and does not require special treatment. Patients can reduce these symptoms through their own regulation and lifestyle changes. In response to these reactions, patients should try to get enough sleep and do some light exercise; pay attention to diet and nutrition, eat less and more easily digestible food, and eat more vegetables and fruits. If a certain symptom is more obvious, the doctor will appropriately cooperate with the effect of drugs to reduce the symptoms. The side effect of systemic reaction is the suppression of hematopoietic function, which can cause the number of white blood cells, platelets or red blood cells in the blood to drop. If there is a significant drop, it may be accompanied by the risk of infection and bleeding. To address this possibility, blood tests must be performed before radiation therapy to understand the hematopoietic function. If one or more of the white blood cells, red blood cells or platelets are significantly lower than normal, radiotherapy cannot be administered and must be administered only after the hematopoietic function has been restored accordingly. During the course of radiotherapy, blood tests should be conducted every week, and if there is a decrease in the corresponding blood cell value, the corresponding drugs to stimulate hematopoietic function can be applied. Because radiotherapy is a local treatment, the side effects of radiotherapy are mainly local reactions. The local side effects usually refer to the damage to the normal organs located around the tumor tissue that inevitably receive a certain amount of radiation. Based on the current level of radiation therapy, it is not possible to avoid that these surrounding normal tissues do not receive radiation at all. Most of the local reactions that occur during radiotherapy or in the first few months after radiotherapy are called early reactions, and most of them can be recovered, and some targeted measures and health care during the treatment play a key role in reducing these side effects. The following we understand the corresponding treatment measures for some common local reactions one by one. 1, skin reactions: two to three weeks after the start of radiotherapy, patients in the radiotherapy area skin will appear dry, pigmentation, burning sensation, hair loss, skin desquamation, itching, and even serious blisters break out. This requires patients to treat the skin in the radiotherapy area very carefully from the beginning of radiotherapy, wear cotton loose clothes, keep the skin in the radiotherapy area clean and dry, avoid using soap and bathing lotion on the skin in the radiotherapy area, do not engage in friction or scratching the sensitive parts, and do not use excessively hot water. Do not apply various powders, creams and skin creams on the skin in the radiotherapy area without the doctor’s consent, and do not expose the skin in the radiotherapy area to the sun. In case of breakout, there is no need to be overly nervous, as the doctor will take appropriate measures to avoid infection and promote healing of the area. Most of the skin reactions will be eliminated a few weeks after the end of radiotherapy, and most of the hair loss after head radiotherapy will grow back again. 2, oral mucous membrane reaction: If the mucous membrane of the mouth and pharynx is located in the radiotherapy area, most of them will have acute oral and pharyngeal mucous membrane reaction, which usually manifests as redness, swelling, ulceration, taste change, pain and difficulty in swallowing of the oral mucous membrane, and some of them will have swollen gums and caries at a later stage. After the salivary glands are irradiated by radiation, dry mouth and decreased oral purification function will occur, and these symptoms are very common in patients undergoing head and neck radiotherapy. Patients are advised to have oral examination before radiotherapy, clean their teeth, and deal with caries and loose teeth. During and after radiotherapy, rinse the mouth with salt water, brush the teeth with a soft-bristled toothbrush in the morning and evening, and avoid eating spicy, fried, hard and hot foods. If there is pain in eating, eat semi-liquid and liquid food. Avoid smoking, alcohol and betel nut, and try to ensure proper caloric protein and vitamin intake. In case of severe reactions, the doctor will apply antibiotics and glucocorticoids. The above measures can usually reduce the oral mucosal reactions after radiotherapy. 3.Radiation pneumonia: When a certain volume of lung tissue is subjected to a considerable amount of radiotherapy dose, coughing, sputum, fever and dyspnea will occur, with symptoms varying in severity, usually with upper respiratory tract infection as the causative factor. Therefore, it is important to check the lung function before radiotherapy and formulate the appropriate dose of radiotherapy. During radiotherapy, patients should pay attention to keep warm and do not get cold, do deep breathing exercises, strengthen nutrition, pay attention to rest and strengthen resistance. 4, radiation esophagitis: two to three weeks after receiving radiotherapy, there will be a burning sensation behind the sternum, swallowing difficulties and other symptoms of radiation esophagitis, patients should avoid eating too hot, too hard and too spicy food to reduce the stimulation of the esophageal mucosa. Eat slowly with few meals and pay attention to the intake of protein, vitamins and calories. If the symptoms are very obvious, antibiotics and glucocorticoids can also be used to reduce the inflammatory reaction and edema of the mucosa and to provide appropriate intravenous nutrition. 5.Radiation gastroenteritis: The acute reaction of the stomach usually includes anorexia, nausea and vomiting, and in severe cases, gastric bleeding and perforation. Acute intestinal reactions are usually manifested as abdominal pain and diarrhea, increased number of stools, etc., while radioactive proctitis has obvious urgency, mucus and blood stools and painful stools, and severe intestinal stenosis and perforation may occur. While trying to control the gastrointestinal dose, patients should eat a light diet with few meals and easy-to-digest foods, and alcohol is strictly prohibited. Can be appropriate to eat honey to keep the stool smooth, constipation can be applied according to the situation of the open road laxative. 6, radioactive cystitis: when pelvic radiotherapy, radioactive cystitis, the main symptoms are pain in the lower abdomen, urination, urinary frequency and urgency, hematuria, painful urination, etc., usually can be controlled, to the end of radiotherapy can return to normal, patients should drink more water and keep the bladder full before radiotherapy can reduce the volume of bladder irradiation. The above are some common early local reactions during radiotherapy, and some very important organs of human body, such as heart, liver, brain, spinal cord, kidney, eyes, etc., including the above early reactions of tissues, usually can tolerate a certain dose and no serious side effects will occur within a certain range, but if the tolerable range is exceeded, irreversible permanent damage often occurs, often manifested as months or years after the end of radiotherapy, i.e. late damage. Therefore, radiotherapy must control the dose of surrounding normal tissues within the tolerable range while treating the tumor, and if the situation allows, adopt precise radiotherapy as much as possible, such as conformal and intensity-modulated radiotherapy which is widely adopted in Hunan Cancer Hospital now, to ensure the necessary treatment dose of tumor tissues while reducing the dose of normal tissues as much as possible, so as to minimize the side effects of radiotherapy and improve the survival time and quality of patients. This can minimize the side effects of radiotherapy and improve the survival time and quality of life of patients. In addition, if the diagnosis is clear, surgery, chemotherapy and bio-immunotherapy can be adopted according to the condition to achieve a more effective treatment. The rapid development of radiotherapy technology and the accumulation of clinical experience give us good reasons to believe that the rational application of this treatment and the corresponding treatment measures can bring good news to the majority of patients.