1.What is radiotherapy? Radiotherapy, short for radiation therapy, is one of the main means of treating tumors, which uses radiation to kill cancer cells so that the tumor shrinks or disappears to treat the tumor. Radiation destroys the cells in the irradiated area (target area) and stops these cells from dividing until they die. The purpose of radiotherapy is to kill tumor cells as much as possible while protecting normal tissues. 2.What tumors need radiotherapy? Current statistics show that about 70% of patients with malignant tumors need radiotherapy at different stages of disease development, but for a specific patient, whether to use radiotherapy should be in accordance with the principle of standardized treatment of tumors, the stage of development of tumors and the patient’s physical condition. Clinically, suitable tumors for radiotherapy include nasopharyngeal cancer, laryngeal cancer, tonsil cancer, tongue cancer, malignant lymphoma, cervical cancer, skin cancer, brain tumor, esophageal cancer, breast cancer, lung cancer, rectal cancer, bone tumors, liver cancer, soft tissue sarcoma and so on. 3.How long does radiotherapy take? According to the nature of tumor and therapeutic purpose, radiotherapy is divided into radical radiotherapy, preoperative radiotherapy, postoperative radiotherapy and palliative radiotherapy. The time needed to complete radiotherapy for different purposes is different, which is described below: Radical radiotherapy: control or even cure the tumor by radiotherapy alone. Some tumors, such as nasopharyngeal cancer, laryngeal cancer, tonsil cancer, tongue cancer, malignant lymphoma, cervical cancer, skin cancer, etc. can be cured by radiotherapy alone. In addition, radical radiotherapy can also be given to those who cannot be operated or those who are unwilling to be operated in the area where the tumor grows. Radiotherapy dose must be sufficient for radical radiotherapy, otherwise it will leave a hidden danger of recurrence. It usually takes 6-7 weeks to complete. Preoperative radiotherapy: because of the large tumor or the adhesion with the surrounding organs that cannot be operated, a part of the dose of preoperative radiotherapy can be used to shrink the tumor and facilitate the operation. It usually takes 3-4 weeks to complete and 3-6 weeks of rest after radiotherapy before surgery. This rest after radiotherapy is for the normal tissues to repair the radiotherapy reaction, and at the same time to make the tumor shrink further to facilitate surgical resection. During the period of radiotherapy and rest, the cancer cells are gradually dying, so don’t worry about whether the cancer cells will grow if the surgery is delayed. Post-operative radiotherapy: Because the tumor grows in a special place or adheres to the surrounding organs and cannot be completely removed, these residual tumors will recur and metastasize after surgery, so radiotherapy should be used to eliminate the residual cancer cells after surgery. The duration of radiotherapy depends on the amount of residual tumor. If there are more residual tumors, the residual tumors can be seen with the naked eye, and almost the same time and dose as radical radiotherapy is needed. If there is less residual tumor and only cancer cells can be seen under the microscope, 2/3 of the dose of radical radiotherapy is usually sufficient, i.e. 4-5 weeks. Palliative radiotherapy: If the patient suffers from pain due to tumor growth, such as pain from bone metastasis, dyspnea caused by tumor blockage or compression of trachea, obstruction of blood return to swelling caused by compression of veins, headache caused by intracerebral metastasis, and danger of paralysis caused by tumor invasion and compression of spinal cord, etc., a certain dose of radiotherapy is given to alleviate the symptoms and relieve the pain. The dose of radiotherapy varies according to the location and purpose of the tumor, ranging from several times to one month. 4.What is external irradiation and what is internal irradiation? According to the proximity of the radiation source, there are two types of radiation: external radiation and internal radiation. External irradiation: also known as long-distance radiotherapy, the radiation is sent to irradiate the tumor from a certain distance outside the human body (e.g. 75cm for cobalt-60 machine and 100cm for linear gas pedal). This kind of radiation has high energy and strong penetrating power, and the tumor can get relatively uniform radiotherapy dose. External radiation is one of the more widely used methods of radiotherapy at present. Internal irradiation: also known as brachytherapy, the radiation source is directly placed into the tumor (particle implantation), or into the adjacent lumen of the tumor (trachea, esophagus, vagina, etc.) for radiotherapy. The radiation source used for internal irradiation has a short range and low penetrating power, the advantage is that the tumor can get a higher dose, and the normal tissues in the remote area are protected by low dose, but the disadvantage is that the dose distribution is not uniform, and it is easy to cause hot spots (too high dose area) and cold spots (too low dose area), which increases the risk of tumor residuals and recurrence. Therefore, except for cervical cancer, at present, internal irradiation is only applied as the supplementary dose of external irradiation, and is not applied alone. 5.What is general radiotherapy? What is stereotactic radiotherapy? Ordinary radiotherapy is a commonly used traditional radiotherapy method, the irradiation scope includes the tumor, nearby metastatic foci, nearby areas to be metastasized, generally irradiated once a day, 5 times a week, each time giving conventional radiotherapy dose. The advantage is that the tumor and nearby lymph node area can be irradiated, and the cost is low. The disadvantage is that the surrounding normal tissues are unnecessarily irradiated, resulting in radiotherapy side effects. Stereotactic radiotherapy, also known as gamma knife or X-knife, is a treatment in which the radiation is focused to the tumor in many different directions, destroying the tumor while protecting the surrounding normal tissues. The result of the treatment is like a knife resection as the tumor necrosis disappears, so the image is compared to a “knife”, gamma (γ) knife (X-knife) is not open surgery! 6, gamma (γ) knife and X-knife what is the difference? Radiotherapy commonly used rays are gamma rays, X-rays, beta rays, etc. Gamma rays are generated by the radioactive element cobalt-60 (or other radioactive elements) spontaneous decay; X-rays from the gas pedal (high-speed electron impact tungsten target). Therefore, stereotactic radiotherapy with cobalt-60 as the radiation source is called gamma (γ) knife, and stereotactic radiotherapy with a gas pedal as the radiation source is commonly known as X-knife. The head gamma knife consists of multiple cobalt-60 radiation sources arranged in a hemispherical device, the rays are focused on intracerebral lesions through a helmet with multiple apertures (collimator), due to the limitations imposed by many factors, the maximum aperture of the helmet can only be up to 18mm, the gamma knife is invasive fixation (rivets will be used to fix the headgear to the skull), usually only once, so it is suitable for intracranial lesions of less than 18mm. The collimator of X-knife can reach up to 50mm, and non-invasive fixation technology (a thermoplastic mask, which softens in hot water and is then placed on the patient’s face, organized into a shape suitable for the patient’s face, and then hardened and fixed when it cools down) is used for the treatment of intracranial lesions, so it facilitates the treatment in several sessions, is suitable for all kinds of volumetric lesions, and is even more advantageous for the lesions that are slightly larger in volume. (Note: collimator: in order to achieve a certain purpose, to be directed by the machine out of the radiation beam limit, play this role of the device called collimator). 7. Is the human body radioactive after radiotherapy? Many patients are worried about the radioactivity of their body after radiotherapy, the answer to this question depends on the radiotherapy method used. General external radiation radiotherapy after the body is certainly not radioactive, because the radioactive source in the body outside a certain distance from the machine. So you can be close to your relatives and friends after radiotherapy. Internal irradiation places the radioactive source in the body, and the organs near the source are radioactive, so care should be taken to protect the surrounding people. Systemic radiotherapy is to inject radioactive elements into blood vessels (e.g., radioactive element strontium treatment of multiple bone metastases), these radioactive elements reach the tumor and other parts of the body with blood flow, and with the body’s metabolism, it will also be discharged into saliva, urine and other secretions, so it is necessary to protect the surrounding personnel and deal with the excretions in a certain period of time. 8.Other radiotherapy methods being applied or being developed Three-dimensional conformal radiotherapy (3DRT): traditional common radiotherapy is two-dimensional (length and width of the tumor) radiotherapy, if using CT, PET, MRI in the direction of the tumor three-dimensional (length, width, depth) according to the irregular shape of the tumor modification of rays for radiotherapy, known as three-dimensional conformal radiotherapy, the advantage of the protection of the surrounding normal tissues. Intensity-modulated conformal radiotherapy (IMRT): On the basis of 3D conformal radiotherapy, the radiation dose is adjusted in a certain way, so as to achieve a uniform radiotherapy dose inside the tumor. Image-guided radiotherapy (IGRT): In the course of radiotherapy, CT image guidance is used to accurately locate the tumor site planned for treatment, further improving the accuracy of tumor treatment. Biological Guided Radiotherapy (BGRT): Tumor cells within the tumor tissue have a certain degree of heterogeneity, and the sensitivity of tumor cells to radiation is also different. According to the biological characteristics of different tumor cells, different radiotherapy doses are chosen to achieve the purpose of eventually killing all tumors. This radiotherapy method is under development. 9. How long does radiotherapy take effect? The effect of radiotherapy cannot be seen immediately after radiotherapy, the tumor cells will start to die a few days or weeks after radiotherapy, and the necrosis of the tumor cells will still last for a few weeks or months after the end of radiotherapy. 10. Is radiotherapy painful? What are the side effects of radiotherapy? Radiotherapy uses radiation to kill tumors, and this high-energy radioactivity is invisible to the naked eye. While killing the tumor cells, the radiation also damages the normal cells within the irradiated area. This damage to normal tissues gradually recovers after radiation therapy is completed. At the beginning of radiotherapy, patients will not suffer from the pain caused by radiotherapy, but with the continuation of radiotherapy, the degree of necrosis of cancer cells will gradually increase, and the degree of damage to normal tissue cells will also increase, and then there will be a corresponding manifestation of damage to normal tissues, which is called the acute reaction of radiotherapy (e.g., radiotherapeutic esophagitis, in which the patient will feel pain in the esophagus when swallowing, etc.). Doctors will deal with these side effects of radiotherapy and should not give up the opportunity of tumor treatment because of this temporary reaction to radiotherapy.