Malignant tumors have become the number one threat to people’s lives in modern society. Surgery, radiotherapy and chemotherapy are still the three major means to treat tumors. Tumor patients and their family members habitually know that surgery is needed when they have tumor, and chemotherapy is needed if they cannot have surgery. Such a treatment plan leads to some patients who could be cured by radiotherapy lose the best treatment time and become incurable, and patients pay the price of life for this. The reason is that patients know little about radiotherapy, and radiotherapy is often reduced to a supporting role of tumor treatment. In 2000, the World Health Organization reported that among all tumor patients cured, nearly half of them were cured by radiotherapy, the other half were cured by surgery, and very few were cured by chemotherapy. It is evident that radiotherapy has a similar therapeutic effect as surgery. The worst thing in clinical practice is to treat inoperable patients with endless chemotherapy until the patient dies. It should be avoided that “chemotherapy does not stop until the patient dies”. It is important to understand that most tumors cannot be cured by a single chemotherapy because of the drug resistance of tumor cells. The essential feature of malignant tumors is metastasis, and once bloodstream distant metastasis occurs, most of the tumors are impossible to be cured. Distant metastasis is related to the early stage of disease, the later the stage of disease, the higher the incidence. Another kind of metastasis in clinical practice is lymph node metastasis, which is different from bloodborne distant metastasis, because lymph node metastasis belongs to local regional metastasis near the primary tumor, these patients may have lost the chance of surgery, but have the hope of being cured by radiotherapy. Since a tumor cannot be cured if blood-borne distant metastasis occurs, the fundamental strategy to cure a tumor is to completely destroy the tumor and the cancer cells in local and regional lymph node metastasis before distant metastasis occurs. This requires early arrangement of radical treatment, i.e. surgery or radiotherapy, in order for patients to have greater hope of cure. Tumors in the body are like time bombs. The later the radical treatment, the greater the possibility of distant metastasis and the less hope of cure. Radiation therapy is a local treatment like surgery, but has a wider range of indications than surgery. Surgery is often used for patients with early to mid-stage tumors. Unfortunately, at the time of diagnosis, only about 30% of patients with early to mid-stage tumors are diagnosed, and up to 40% of patients with inoperable locally advanced disease have the only hope of cure with radiotherapy. For example, in laryngeal cancer, surgery often requires removal of the larynx and the patient cannot speak after surgery, while radiotherapy does not affect the speech function, and the efficacy of both is the same. Therefore, many tumors, especially head and neck tumors, can often be treated with radiotherapy rather than surgery. Compared with developed countries such as the United States, the percentage of tumor patients in China who prefer radiotherapy treatment is relatively low, which means that some tumor patients are not treated according to international standard treatment, and their efficacy is conceivable. The National Comprehensive Cancer Network (NCCN) publishes various tumor treatment guidelines (NCCN guidelines for short) to the world every year, which is the standard protocol to guide the treatment of various tumors and is widely accepted and recognized by oncologists all over the world. According to the NCCN guidelines, radiotherapy is widely used in the treatment of various tumors: it can be the first choice of treatment for tumors, or postoperative treatment, or preoperative treatment, etc. It is impossible to list them all here. Radiotherapy has been used to treat tumors for more than 100 years. Modern radiotherapy technology has developed to the era of precision radiotherapy. Compared with traditional conventional radiotherapy, precision radiotherapy further improves tumor efficacy, reduces radiotherapy complications, improves patients’ quality of life, and cured patients live and work as normal people.