Radiation therapy for tumors, referred to as radiotherapy, is a method of treating malignant tumors by using radiation such as alpha, beta, gamma rays produced by radionuclides and x-rays, electron rays, proton beams and other particle beams produced by various types of x-ray therapy machines or gas pedals. In the treatment process of all tumor patients, 60-70% have received radiation therapy. Among 45% curable malignant tumors, 18% are cured by radiation therapy, which shows the importance of radiation therapy in the treatment of malignant tumors. Modern tumor treatment requires comprehensive treatment and rational and planned application of existing treatment means in order to achieve the best therapeutic effect. Radiotherapy is the main treatment means or an indispensable part of comprehensive treatment for many malignant tumors, including the following: 1. Head and neck tumors First of all, nasopharyngeal carcinoma, radiotherapy is the only radical treatment for nasopharyngeal carcinoma, for the following reasons: nasopharyngeal carcinoma has a special anatomical location and there are a lot of important organs next to it, which makes surgery risky, and surgery is destructive to the head, neck and maxillofacial structures. The rapid development of the disease brings difficulties and limitations to surgery. Ninety percent of nasopharyngeal carcinomas are low-differentiated squamous epithelial cell carcinomas, which are quite sensitive to radiotherapy. Radiation can simultaneously irradiate the primary foci, infiltrating foci and more distant lymphatic metastases to achieve the purpose of radical treatment. In early laryngeal cancer, the vocal function is close to normal after radiotherapy for early laryngeal cancer. Even for patients who fail radiotherapy, radical tumor cure may still be achieved through surgery. Therefore, radiotherapy is the first choice for early laryngeal cancer. Radiotherapy can achieve good disease control and function preservation for early active tongue cancer, low differentiated tonsil squamous carcinoma and undifferentiated carcinoma. For poorly differentiated and radiotherapy-sensitive early oropharyngeal and hypopharyngeal cancers, which cause swallowing and vocal dysfunction after surgery, radical radiotherapy can be chosen at present. Head and neck squamous carcinoma, with complex anatomical structure of head and neck, is usually very traumatic to operate alone and causes great damage to patient’s body function and facial appearance, so reasonable arrangement of surgery and radiotherapy can reduce the damage and achieve better curative effect. 2.Thoracic tumor Early stage lung cancer can achieve similar treatment effect as surgery with stereotactic radiotherapy, so radiotherapy is the first choice for such patients. For locally advanced lung cancer, radiotherapy should also be preferred if the chance of surgery is lost, and some patients can also get better results. In advanced lung cancer, airway blockage, blood vessel compression causing breathing difficulty, brain metastasis and painful bone metastasis can be treated well by radiotherapy. For esophageal cancer occurring in the neck and upper thoracic region, radiotherapy is as effective as surgery, with relatively less damage to human body and higher quality of life after treatment, so radiotherapy can be preferred. Radiotherapy should also be chosen for locally advanced esophageal cancer with lymph node metastasis that cannot be completely removed by surgery, which can relieve or improve the symptoms of esophageal cancer feeding obstruction. For breast cancer patients who underwent modified radical surgery, postoperative radiotherapy can reduce the local recurrence rate and improve the long-term survival rate for those with cancer foci larger than 5 cm, invading the skin of chest wall or having lymph node metastasis, and such patients should undergo postoperative radiotherapy after surgery. In principle, all patients after breast-conserving surgery should undergo postoperative radiotherapy to improve the efficacy. 3.Malignant lymphoma Malignant lymphoma refers to a group of diseases originating from the lymphatic system. The treatment of most malignant lymphomas requires the participation of radiotherapy, which has a better sensitive effect. The treatment of lymphoma such as nasal NK/T cell lymphoma and early mycosis fungoides is more radiotherapy oriented. In addition, radiotherapy is the radical treatment for early stage (I-II) inert lymphoma. 4, abdominal and pelvic tumors Rectal cancer, postoperative radiotherapy for rectal cancer that invades the rectal epithelium or has lymph node metastasis can reduce the recurrence rate, and simultaneous radiotherapy can improve the survival rate of patients, which is recommended as standard treatment; preoperative radiotherapy for rectal cancer can reduce the clinical stage, increase the tumor resection rate and anus preservation rate, improve the local control rate of tumor, and improve the quality of life of patients. Radiotherapy is also the main treatment for cervical cancer, and internal irradiation combined with intracavitary rear-loading irradiation can achieve good disease control. For limited stage, locally advanced prostate cancer and early testicular seminomatous cell tumor, radiotherapy is the radical treatment method. 5.Other The recurrence rate of soft tissue sarcoma is high after surgery, and postoperative radiotherapy is required in most cases. Malignant glioma, regardless of whether the surgery is completely removed or not, postoperative radiotherapy can reduce local recurrence and improve survival rate. Brain metastases, patients with brain metastases often have headache and activity disorders, which seriously affect the quality of life. Most patients with bone metastasis pain can be significantly relieved or improved after radiotherapy. If tumor patients have tumor emergencies such as superior vena cava compression syndrome and spinal cord compression, emergency radiotherapy can quickly relieve the symptoms and relieve patients’ pain.