Currently, the incidence and mortality rate of lung cancer is the highest among all cancers. In China, 70% or even 80% of lung cancer patients are already in the middle or late stage when diagnosed and cannot receive surgery. The current treatment of malignant tumors mainly relies on three main treatment methods, such as surgery, radiotherapy and chemotherapy. The relative contribution of these three major treatment means to tumor treatment are: 22% (48.9%) of malignant tumors can be cured by surgery, 18% (40%) of malignant tumors can be cured by radiotherapy, and 5% (11.1%) of malignant tumors can be cured by chemotherapy. Of course, with the continuous progress of basic research on tumor, the continuous updating of radiotherapy treatment equipment, and the emergence of new targeted drugs, it is expected that more early malignant tumors will be controlled or cured. As the deputy director of Heilongjiang Cancer Institute, the executive member of Chinese Medical Association Radiation Oncology Branch, the director of Heilongjiang Radiation Oncology Society and Provincial Anti-Cancer Association Radiotherapy Committee, Xu Xiangying, the director of Radiotherapy Department of Cancer Hospital of Harbin Medical University, said: “Radiotherapy is one of the main means of comprehensive treatment for malignant tumors. It can be applied to lung cancer and other malignant tumors alone, or in combination with surgery and chemotherapy to improve the local control rate and long-term survival. When it comes to the lung cancer radiation therapy and comprehensive treatment that Dr. Xu Xiangying specializes in, Dr. Xu introduces that a large number of domestic and foreign evidence-based medical studies have concluded that lung cancer requires the participation of radiation therapy at different stages of its treatment. For example, 53.6% of small cell lung cancer patients need radiotherapy in the first course of treatment, 64.3% of non-small cell lung cancer patients need radiotherapy in the first course of treatment; 45.6% of small cell lung cancer patients need radiotherapy in different stages of the disease, while 45.9% of non-small cell lung cancer patients need radiotherapy in different stages of the disease. Radiotherapy is a means of localized killing of cancerous lesions and is quite widely used in lung cancer treatment. Most lung cancer cases with extensive lesions at the time of definite diagnosis, distant metastases or poor systemic conditions that are not suitable for surgical treatment should consider radiotherapy, which can better control the tumor and prolong the survival. If a patient with lung cancer has no special medical comorbidities and receives only surgery, radiotherapy or chemotherapy, it is obviously not in line with the treatment principle of lung cancer. Precise radiotherapy – accurately killing tumors and reducing normal tissue damage In the treatment of lung cancer, radiotherapy is an indispensable and important treatment tool. It can improve the local control rate of lung cancer, reduce local recurrence and improve long-term survival. Previously, radiotherapy using ordinary external irradiation technique has achieved good efficacy, but due to the large damage to normal tissues and obvious side effects, it has seriously limited the application of radiotherapy. In recent years, three-dimensional conformal radiation therapy (3DCRT) and intensity-modulated radiation therapy (IMRT) are high-tech radiation therapy techniques applied to tumor radiation therapy, which means that the shape of the irradiation field is exactly the same as the actual shape of the tumor in the three-dimensional direction, and in addition, the irradiation dose at any point inside the irradiation field is exactly equal, and the surrounding normal tissues receive significantly less dose. Because of the higher requirements and more precise scope of treatment, the treatment is performed by first individualizing the fixation of the body film, body frame or vacuum pad, followed by a thin-layer scan under a CT analog localization machine, and the images obtained are transmitted to the treatment planning system, where a physician outlines the tumor area that should be treated, the surrounding subclinical areas, and the important functional areas that need to be protected. The treatment plan is calculated by a professional physicist, and the ideal treatment plan is finally implemented on the treatment machine. The advantages are accurate positioning, radiation only irradiates the tumor area, and produces little or no major side effects on the normal tissues or functional organs around the tumor. The indications for radiation therapy for some patients with poor lung function and advanced age have been relaxed. Due to the mild treatment damage, 3D conformal radiotherapy and intensity-modulated radiotherapy can increase the local treatment dose of the tumor and achieve the purpose of improving the local control rate. Professor Xu Xiangying also talked about: an important issue in radiotherapy is the determination of radiation dose. The size of radiation dose for tumor should generally be decided according to the pathological type of tumor, the size of radiation field, the condition of tumor surrounding tissues, the nature of radiation and patient’s tolerance level, the degree of lesion regression after treatment and the minimum recurrence rate that may be obtained. Since the local control rate of tumor depends on the radiation therapy dose, i.e., increasing the local radiation therapy dose and the local tumor control rate are proportional. Three-dimensional conformal radiotherapy irradiates the tumor in an accurate range and causes less damage to the normal tissues around the tumor, therefore, the dose of radiation can be appropriately increased for suitable patients, which can achieve the effect of improving the local control rate of lung cancer. Generally speaking, once the purpose of radiotherapy is clearly defined, the dose, number and duration of each radiation treatment can be basically determined, and the treatment plan and additional treatments can be precisely designed to achieve the best therapeutic effect within the prescribed dose. In order to avoid unnecessary side effects, it is not advisable to increase the radiation dose arbitrarily. We should pay attention to the fact that only one course of radiotherapy can be given to each specific part of the human body, and for this reason, radiotherapy should be given on time in order to achieve the ideal immediate curative effect and to strive for radical treatment. It is known that more than 50% of lung tumors will move more than 5m with respiratory movement during radiotherapy, thus causing the leakage of tumor target area and increasing the irradiated volume of normal tissues. CT scans of the lower lung tumors were performed in the patient’s free-breathing state, and the results showed that the average displacement of the lower lung lobe tumors was 9.1 mm (3.4 to 24.0 mm) in the head-foot direction and 10.1 mm (0 to 22.0 mm) in the left-right direction, and the average displacement of the upper middle lobe tumors was 6.2 mm (2.4 to 11.3 mm) in the head-foot direction. The average motion of lower lobe lung tumors was greater than that of tumors in other locations of the lung, and the displacement in the head-foot direction was the most significant. In view of the above reasons, the image guided radiotherapy (IGRT) technique, which is being widely carried out in China and abroad in recent years, takes into full consideration such factors as the breathing of the lung and the peristaltic motion of the abdominal organs, the positioning error during daily radiotherapy and the contraction of the tumor target area during treatment, which cause the movement and error during the treatment process and between treatment sessions, and cause the change of radiotherapy dose distribution and the impact on the treatment plan. In addition, the radiation dose distribution and the impact on the treatment plan will be changed due to the contraction of the tumor target area during the treatment process and between treatment fractions, etc. Before and during the patient’s treatment, the lung tumor and normal organs will be monitored and the treatment conditions will be adjusted in a timely manner through the implementation of various modes and fusion images such as 4-dimensional-CT scanning, so that the irradiation field will change closely with the target area and the irradiation target area will be more precise. Adverse effects on normal tissues are within tolerable limits, looking to improve local control rates and survival of tumors. Importance of image-guided radiation therapy During radiation therapy for lung cancer, some uncertainties affect the distribution of the actual irradiation dose to the tumor, resulting in off-target tumor and/or increased damage to normal tissues. (1) Displacement of tumor and surrounding normal organ tissues, including inter-treatment and intra-treatment position changes. Inter-treatment displacement mainly refers to organs close to the digestive and urinary systems, with different degrees of displacement with the state of the gastrointestinal tract and bladder and changes in patient weight. Intra-treatment displacement mainly refers to the effect of respiratory movements, heartbeat and involuntary muscle contractions on the thoracic and abdominal organs during irradiation. â‘¡Positioning error is an important factor affecting the accuracy of radiotherapy, even for head and neck tumors that are better fixed. The inconsistency in shape between the positional equipment, CT and treatment bed, and the inconsistency in cushioning capacity due to different materials make systematic errors between the patient’s positional position and the planned body position. The width of the body surface scratches and technician factors make random errors between the treatment position and the planned position of the patient each day. (iii) There is a risk of incorrect information transmission during the diagnostic imaging and planning phase and the actual treatment phase as well as errors in the design, markings or position of treatment aids such as compensators, blocks and braking systems. If organ motion, deformation and various errors deviate the tumor (target area) and endangered organs from the field, there will be underdose of tumor and overdose irradiation of endangered organs. â‘£ During radiotherapy, the volume of the tumor will change with the increase of irradiation dose, so that the normal tissue is exposed to an increased amount. The patient’s own factors (weight change during treatment, etc.) can also cause a mismatch between the irradiation field and the location of the target area. To solve these problems, radiation therapy machines are combined with imaging equipment to acquire relevant image information during treatment, determine the location and motion of the treatment target area and important structures, and perform correction of the location and dose distribution when necessary. Therefore, image-guided radiation therapy (IGRT), a four-dimensional advanced precision radiotherapy technique, not only adds the concept of time factor to the three-dimensional radiotherapy technique, but also takes into full consideration the movement of anatomical tissues during treatment and the displacement errors between fractional treatments, such as respiratory and peristaltic movements, daily positional errors, target area contraction, etc., which cause changes in radiotherapy dose distribution and impact on treatment planning We use various advanced imaging devices to monitor the tumor and normal organs in real time before and during treatment, and can adjust the treatment conditions according to the changes in the position of the organs so that the irradiation field can closely follow the target area, making it possible to achieve truly precise treatment. Precise irradiation ensures higher dose of radiotherapy – promises to prolong survival of lung cancer Doctors: In the past, the lack of perfect imaging and imprecise target area outlining caused different degrees of errors in target area outlining. As a result, the target area of tumor irradiation is larger, and the radiotherapy dose for tumor cannot or cannot be improved, which affects the long-term survival of lung cancer. Image-guided radiotherapy technology can adjust the planned target area of lung cancer radiation therapy every week during radiotherapy to maximize the local dose of tumor irradiation while reducing the damage to normal tissues, and ensure the accurate dose of tumor irradiation for tumors with complex shapes and in motion, so that the position of the patient’s target area during treatment is more consistent with the position of the target area in the radiotherapy plan, reducing the dose to normal lung tissues and tumors. This can further improve the local control rate of lung cancer and prolong the long-term survival of lung cancer.