I. The status of radiotherapy in tumor treatment Malignant tumor is a kind of multi-morbidity and common disease, which has seriously threatened people’s life and health. Since the 1970s, the incidence of malignant tumors has been on the rise. According to WHO, the number of new cancer cases worldwide was about 8.07 million in 1990, which was 37.4% higher than 5.17 million in 1975; the number of cancer deaths worldwide was about 6.2 million in 1997. If the current trend is followed, by 2020, with the population reaching 8 billion, there will be 20 million new cases worldwide, of which the death rate will reach 12 million. According to statistics, the total incidence rate of cancer in China is about 200/100,000, and the total mortality rate of cancer is about 110/100,000. Currently, there are more and more treatments for tumors, but surgery, radiotherapy and chemotherapy are still the three most effective main treatments. According to the statistics of major tumor treatment centers in China, about 70% of patients need to receive radiotherapy, while in foreign countries, such as the United States and Japan, those who receive radiotherapy account for about 50-60% of new cases in the year, and there is still a rising trend. With the development of science, the cure rate of tumor is also gradually improving. WHO announced that the overall cure rate of three major means combined is 45%, among which surgery accounts for 22%, radiotherapy accounts for 18% and chemotherapy accounts for 5%; among 55% of patients who are not cured, 18% are locally uncontrolled and 37% are distant metastases, and among these uncontrolled and distant metastases, the vast majority of cases need radiotherapy at some stage. Thus, it can be seen that the contribution of tumor radiotherapy as an important treatment tool is self-evident. The mechanism and principles of radiotherapy (a) The mechanism of radiotherapy From the basis of molecular biology, the treatment of tumor by radiation mainly relies on the ionizing effect of radiation, which causes damage to the DNA structure, resulting in cellular ultrastructure damage or destruction, and then causes changes in cell morphology and tissue reaction. Specifically, the mechanism of action of ionizing radiation can be summarized into two main types: direct action and indirect action. The direct action refers to the direct ionization of organic molecules (represented by RH) in human tissues by radiation, and the generation of free radicals R. This causes biological damage. This damage can be repaired by the action of sulfhydryl (-SH) compounds, but if there is oxygen in the tissue, R. can combine with oxygen to form RO2. and make molecular damage, and it is not easy to repair. The so-called indirect action: refers to the damage caused by ionizing radiation to organic molecules of human tissues by indirect means. As we all know, the main component of biological organism is water, when water is affected by ionizing radiation, it can be ionized, producing H2O+, H+, OH-, H3O- and free electrons, and can produce very active free radicals OH., H., HO2. and H2O2 with super oxidizing ability, these products can damage the normal molecular structure and make the biological target damaged. From the perspective of tumor treatment, the therapeutic effect of radiotherapy as a treatment means on tumor is mainly reflected in the following three aspects: 1. Radiotherapy can directly cause tumor cell damage including lethal damage, sublethal damage and potentially lethal damage. 2.Radiotherapy can inhibit the regeneration of tumor blood vessels and close small blood vessels and lymphatic vessels. 3.Radiotherapy can cause inflammatory response at the irradiated site, induce immune cells to enter the irradiated area and enhance phagocytosis of tumor cells. However, with the increase of radiation therapy dose, this effect will be greatly weakened. （The principles of radiotherapy are summarized in four points: 1. the scope of irradiation should include the tumor; 2. to achieve the purpose of basic tumor destruction; 3. to protect the adjacent normal tissues; 4. to maintain a good general condition and mental state 3. radiotherapy modalities Radiotherapy modalities can be divided into two categories: external irradiation and internal irradiation. External irradiation is divided into: conventional external irradiation and precise external irradiation. Conventional external radiation is generally irradiated in two-dimensional direction, while precise radiotherapy controls the dose distribution in three-dimensional direction, so that the high-dose area and the treatment target area can coincide. At present, in addition to 3D conformal radiotherapy (including conformal intensity modulated radiotherapy), there are also various “knives”, such as “γ-knife”, “X-knife”, “neutron knife”, etc. In general, internal irradiation is only used as a supplement to external irradiation, but in some cases, internal irradiation can be used alone, such as particle implantation alone for early stage prostate cancer, which can achieve the same efficacy as surgery and has fewer side effects than surgery. In some cases, internal irradiation can also be used alone. Radiation therapy is used as the main radical treatment to cure the tumor. However, in the process of radiotherapy, if the disease changes (such as distant metastasis), the treatment response is larger than expected or other reasons, it can be changed to palliative treatment or comprehensive treatment. Generally, radical radiotherapy is mainly used for skin cancer, nasopharyngeal cancer, acoustic cancer, early esophageal cancer, early non-small cell lung cancer, early cervical cancer and certain brain tumors such as pituitary tumors. It is divided into two types: high palliative and low palliative. The former is to prolong life, and after treatment, patients can live with tumor for many years or even work normally (such as middle and late stage cervical cancer), while the latter is mainly to relieve pain, which often cannot achieve the purpose of prolonging life, and is mostly used to relieve pain (such as bone metastasis), relieve or relieve compression (such as spinal cord compression, etc.), obstruction (such as esophageal cancer, gastric cancer, etc.), bleeding (such as cervical cancer) and brain metastasis symptoms. In the process of palliative radiotherapy, the plan should be adjusted timely according to the condition. If low palliative treatment is very effective, it can be changed to high palliative, while high palliative treatment is very effective, it can also be changed to radical radiotherapy. However, if palliative radiotherapy is expected to be very ineffective or cannot relieve the symptoms, radiotherapy should not be reluctantly used or reluctantly used in larger doses. Integrated therapy refers to the combination of radiotherapy and other therapies to achieve the most effective treatment of tumor. Integrated therapy is the trend of tumor treatment, especially with the increasing science and maturity of various tumor treatment methods, there are more and more explorations and experiences on integrated therapy. The combination with surgery includes preoperative, intraoperative and postoperative radiotherapy and the combination of any two of them, but mostly the combination of preoperative and postoperative radiotherapy. （For example, preoperative radiotherapy can increase the rate of anus preservation in low rectal cancer without increasing the rate of local recurrence, which greatly improves the quality of life of patients. In the past, many surgeons worry that preoperative radiotherapy may delay the operation time and may cause difficulties in surgery, and even think that radiotherapy may increase the difficulty of surgery. In the past, many surgeons were worried that preoperative radiotherapy might delay surgery, might cause difficulties in surgery and increase the difficulty of surgery, and even thought that radiotherapy could make patients’ immunity decline and promote metastasis. At present, this concept has basically changed, because a large number of basic and clinical studies have found that preoperative radiotherapy can not only shrink the tumor and form a pseudo-envelope to make the surgery easy to remove, but also reduce the tumor blood flow and intraoperative bleeding, and at the same time, radiotherapy can also reduce the tumor cell viability, make the tumor downgrade and downgrade the stage, and reduce the local implantation rate and distant metastasis rate. In addition, it has been proved that for the smaller area of low-dose radiotherapy, the radiotherapy dose of about 40Gy will not cause the obvious decrease of immune function. Of course, attention should be paid to the interval between preoperative radiotherapy and surgery, generally 2 to 4 weeks is appropriate. Pre-operative radiotherapy is often used for middle and late stage head and neck cancer, cervical cancer, endometrial cancer, rectal cancer, late stage breast cancer, etc. (2) Post-operative radiotherapy has the advantage of reducing local recurrence rate and regional lymph node metastasis rate. Postoperative radiotherapy is much more effective for residual subclinical lesions than clinically detectable recurrent tumors. Some people even advocate radiotherapy as soon as the incision is well healed and the stitches are removed. The reason for early postoperative radiotherapy is twofold: one is to rush the postoperative fibrous scar formation, because after tumor removal, if local scars are formed, it will affect the blood supply, thus leading to lack of oxygen and reduced radiosensitivity. The second is to avoid tumor recurrence due to rapid proliferation of residual tumor cells again. Postoperative radiotherapy is more common nowadays, and all kinds of tumors need postoperative radiotherapy as long as the disease stage is late, the cut edge is not exhausted or residual is suspected. For example, postoperative radiotherapy is routinely performed for mid- to late-stage endometrial cancer, breast cancer, lung cancer and so on. (3) Intraoperative radiotherapy refers to one-time high-dose irradiation during surgery, so that the irradiated target area has relatively high dose while the normal tissues are less irradiated. Generally, intraoperative radiotherapy is suitable for cases that cannot be completely resected by surgery, and a special light-limiting cylinder is used to irradiate squamous carcinoma and adenocarcinoma with 30-35Gy and 30-40Gy at one time. In principle, intraoperative radiotherapy is applicable to many tumors, but because it requires certain equipment, it is not carried out much in China at present, and is mostly limited to gastric cancer and colorectal cancer. Combination with drugs These drugs include chemotherapeutic drugs, radiosensitizers, biological response modifiers, gene therapy drugs, traditional Chinese medicine, etc. Among them, the combination of radiotherapy with chemotherapeutic drugs and traditional Chinese medicine is the most developed. (1) Combination with chemotherapy drugs: There are two forms of combination of chemotherapy and radiotherapy, one is to use small doses of chemotherapy drugs regularly to sensitize radiotherapy, and the other is to use sufficient amount of chemotherapy and radiotherapy alternately or simultaneously, in order to produce synergistic effects. At present, the study of radiotherapy combination has been widely carried out in lung cancer, breast cancer, nasopharyngeal cancer, esophageal cancer, colorectal cancer, lymphoma and other tumors, and good experience has been gained. (2) Combination with traditional Chinese medicine: At this stage, the role of traditional Chinese medicine mainly has three points: one is to enhance radiosensitivity, the other is to reduce radiotherapy response, and the third is to have synergistic anti-tumor effect with radiotherapy. (3) Other biological response modifiers such as interleukin, interferon and necrosis factor can enhance the anti-tumor effect and immune function of patients, and improve the tolerance to the side effects of radiotherapy, especially it is worth mentioning that gene therapy, although it is in the initial stage, is likely to be the development direction of future breakthrough in tumor treatment. 3.Cooperation with heat therapy High temperature (>43oC) can kill tumor cells. S-phase cells which are insensitive to radiotherapy are most sensitive to high temperature, and high temperature can also kill lack of oxygen cells which are resistant to radiation, which has complementary effect with radiotherapy. In the course of tumor patients, sometimes some acute cases must be dealt with immediately. For some acute conditions, radiotherapy is one of the most effective means to relieve them. These emergencies include: 1. Bleeding: bleeding caused by tumor necrosis is often ineffective with conventional hemostatic methods and can only be stopped naturally after the tumor has subsided. For example, the hemorrhage of cervical cancer and lung cancer can only be temporarily stopped by general drugs and compression, while the hemorrhage will be well stopped after several times of radiotherapy. 2.Superior vena cava syndrome: lung cancer and mediastinal tumor are prone to cause superior vena cava totalis. When patients visit the clinic, the face and neck are swollen, jugular veins and skin veins of chest wall are angered, and they have serious respiratory difficulties. At this time, although impact chemotherapy has certain efficacy, it is mostly not as direct and obvious as radiotherapy. 3.Pulmonary atelectasis: for the extensive pulmonary atelectasis caused by the compression of lung cancer, emergency radiotherapy can improve the dyspnea significantly, and if the treatment is timely, the reopening rate of pulmonary atelectasis can be as high as about 88%. 4.Intracranial hypertension or intraspinal compression: For intracranial hypertension or spinal cord compression caused by primary or metastatic tumor, radiotherapy is one of the most effective treatment methods, and sometimes radiotherapy can show miraculous effect immediately. 5.Anti-pain: For severe pain caused by direct invasion of tumor or bone metastasis, radiotherapy is one of the best treatment methods, and the efficiency of analgesia can be more than 80%. 6.Relief of mass compression and obstruction: such as dysphagia caused by esophageal cancer, extramedullary plasmacytoma, laryngeal obstruction caused by laryngeal cancer, etc. can be relieved by radiotherapy. In the past, the combination of large amount of chest and ascites was also an absolute contraindication, but nowadays, low-dose whole chest or whole abdomen radiotherapy can be carried out. According to the experience of our hospital, interventional chemotherapy combined with whole liver radiotherapy of 2000 cGy, followed by localized three-dimensional conformal irradiation can achieve better results for some advanced liver cancers. However, for patients with gastric lymphoma who are inoperable or unwilling to be operated, chemotherapy plus whole gastric low-dose radiotherapy of 3000 cGy can achieve very good efficacy or even cure, and the reaction can be tolerated. The specific dose of radiotherapy is an issue that every radiotherapist pays more attention to, but sometimes some patients may undergo radiotherapy and chemotherapy at the same time, so it should be noted that the dose of radiotherapy and the dose of chemotherapy drugs must be adjusted appropriately. In general, the dose of chemotherapy drugs and radiotherapy need to be reduced on one side or at the same time, but the specific reduction should depend on the patient’s condition. At present, the combination of radiotherapy and other means is a general trend, especially the combination with surgery and chemotherapy, which has received more attention. However, there is still no unanimous opinion on how to arrange the timing of radiotherapy, surgery and/or chemotherapy. However, generally speaking, preoperative radiotherapy is usually administered at 3000 cGy/10 or 4000 cGy/20 times, and surgery is performed after 2-4 weeks of rest, such as most preoperative radiotherapy for rectal cancer and cervical cancer. Post-operative radiotherapy can be chemotherapy followed by radiotherapy or radiotherapy followed by chemotherapy, depending on the patient’s condition. However, one point must be noted that postoperative adjuvant therapy should be carried out as early as possible, preferably within 2 to 4 weeks after surgery. 4.Radiotherapy side effects As a kind of tumor treatment, radiotherapy naturally cannot avoid the problem of its side effects on normal tissues. Generally speaking, radiotherapy reactions are divided into two categories: acute reactions (immediate reactions) and chronic reactions (delayed reactions). Acute reactions are reactions that occur during radiotherapy and can vary from person to person and from one radiotherapy site to another. It is worth noting that when radiotherapy is combined with chemotherapy and thermotherapy, the side effects of both must be considered comprehensively, and try not to let the same side effects of two treatments at the same time, and if it is really necessary, the dosage should also be considered. For example, if head and neck radiotherapy is combined with 5-Fu-based chemotherapy, oral ulcers will probably be very serious. Some studies have shown that even if radiotherapy is applied simultaneously with 5-Fu sensitization for nasopharyngeal carcinoma, the grade 3 oral mucosal reactions of patients can rise from 0-5% to about 30% in radiotherapy alone. Chronic reactions are reactions that appear weeks or even years after radiotherapy, also called delayed reactions, including early-onset delayed reactions and late-onset delayed reactions. Early-onset delayed reactions refer to reactions that appear several weeks to about 3 months after radiotherapy. For example, central nervous system symptoms and signs such as dizziness, drowsiness and leukocytosis in cerebrospinal fluid can appear within 3 to 4 months after radiotherapy, and some radiation pneumonia also appears 2 to 3 months after radiotherapy. Late onset delayed reactions refer to reactions that appear months to years after radiotherapy. For example, radiomyelitis appears several months to 1 year after radiotherapy, and radiological osteitis and osteonecrosis appear 2 to 3 years after radiotherapy. Some of the side effects of radiotherapy are the price that must be paid for the treatment of tumors, but some of them can be avoided. Therefore, in the process of radiotherapy, the gains and losses of radiotherapy should be fully evaluated, and the treatment plan should be carefully designed in order to achieve better results without overkill and maximize the quality of life of patients.