Radiation therapy is one of the three major clinical tumor treatments (surgery, radiotherapy and chemotherapy) at present. Its advantages are as follows: 1. It has a wide scope of application and can treat almost any tumor in all areas. 2. Patients who cannot tolerate other therapies because of their age, poor physical condition or multiple surgeries can receive radiation therapy. 3.The effect of treatment is reliable and the treatment method is reliable. 4.The treatment process is simple, painless and does not necessarily require hospitalization, which is easily accepted by patients. 5.The treatment has fewer side effects, avoiding anesthesia accidents caused by surgery, blood transfusion reaction, postoperative infection, and side effects such as hair loss and vomiting caused by chemotherapy. 6.Radiotherapy is non-invasive treatment and can preserve the physiological function of the diseased organs.