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Radiation is defined as the emission and propagation of energy. Treating diseases using high-energy rays is called radiotherapy. Radiotherapy is also known as "ray" or "irradiation" treatment. The radiation used in radiation oncology is ionizing radiation. Ionizing radiation is a type of radiation that removes electrons from atoms, causing the atom to become ionized, and damages cells through the chain of biological events that follows ionization. X-rays, gamma rays and charged particles are the types of ionizing radiation used in treatment. This energy was first used to detect diseases inside the body. Later, it was found that radiation used at certain doses has the ability to treat some diseases. Today, radiation is used for diagnostic purposes and is also widely used in the treatment of cancer and, less often, some other diseases.

Radiation therapy can be applied with curative or palliative intent. With curative treatment, the aim is to eliminate the cancer completely and for patients to regain their former health. In cases where cure is not possible, palliative treatment aims to correct or relieve the symptoms caused by the cancer (pain, bleeding, shortness of breath, etc.). The purpose of radiation therapy is to kill the cancer cells in the area where it is applied or to prevent them from dividing and multiplying. Because cancer cells divide and grow faster than the normal cells in our body, they are affected by radiation more quickly. Therefore, when radiation is applied to a cancerous area, many cancer cells are destroyed while fewer normal cells are affected by the radiation. Radiation therapy can be used before surgery (neoadjuvant or preoperative radiotherapy) to shrink the tumor and reduce side effects, and it can also be used after surgery (adjuvant or postoperative radiotherapy) to destroy cancer cells remaining in the operated area.

Radiation oncologists, medical physicists, dosimetrists, technicians, nurses and secretaries work in radiotherapy departments.

After radiation therapy has been decided on, the first step is the simulation procedure, in which the treatment area is determined and marked. In the simulation procedure, an X-ray machine or, more often, computed tomography devices are used to determine the treatment fields. For accurate planning, images must be taken in the same position as the patient's treatment position. For this, the patient needs to lie on the simulator table and remain still for a certain period. For this purpose, depending on the location of the tumor in the body, various custom-made devices (thermoplastic head-and-neck mask, lung holder, knee support, special vacuum beds that can take the shape of the body, etc.) are used that keep the patient still during treatment and increase the patient's comfort while lying down. The simulation procedure can usually take between 15 minutes and 1 hour.

After the simulation procedure, the patients' computed tomography images are transferred to the treatment planning computers. Then, the target volumes to be treated and the normal tissues adjacent to these structures that should not be exposed to radiation are contoured by the radiation oncologists. This is followed by the treatment planning process carried out by the medical physicists. In the final stage, the treatment plans are evaluated by the physician, and the plans that cover the targets best are selected while trying not to exceed the limit values set for normal tissues.

External radiation therapy is most often given in radiation oncology outpatient clinics without hospitalization. In this form of treatment, high-energy radiation is delivered to the cancerous area from outside the body by machines. The treatment machines commonly used in external radiation therapy are "linear accelerators" (LINAC). In these machines, high-energy radiation is produced with accelerated electrons.

The most frequently used external treatment approach today is 3-dimensional conformal radiotherapy. Other treatment modalities that cover target volumes better and spare critical organs better include intensity-modulated radiotherapy (IMRT), image-guided radiotherapy (IGRT), tomotherapy, stereotactic radiosurgery or radiotherapy (Gammaknife, Cyberknife, etc.) and proton therapy. With rapid advances in technology, radiotherapy can be given increasingly effectively and safely, and success rates in cancer treatment are steadily rising.

Stereotactic radiosurgery or radiotherapy is the delivery of a high dose of radiation in a single session or a few fractions to a stereotactically marked target volume. In this method, which is the most advanced conformal treatment technique, beams are directed at the target volume from many different angles, and while high doses are reached in the area where the beams overlap, a rapid dose fall-off is achieved in the normal tissues outside the target volume. Significant advantages in dose distribution over other radiotherapy techniques are provided, particularly for target volumes smaller than 4 cm. With the Cyberknife® device available in our department, stereotactic radiosurgery or radiotherapy can be applied in the treatment of cranial and extracranial tumors.

In brachytherapy (internal radiotherapy), the radioactive source is placed directly into the tumor (interstitial) or into body cavities (intracavitary, etc.). Brachytherapy can be given alone or together with external radiotherapy in the treatment of cancers of the cervix, uterus, breast, prostate, lung, etc. Today this procedure is mostly carried out with the help of remote-controlled afterloading devices. During the procedure, the radioactive source is sent through a special connecting tube, and after the procedure the radioactive source is drawn back into the device.

Radiation therapy can be given in two ways: external and brachytherapy. The treatment machines are located in special rooms for radiation protection and are controlled by technicians from the control room. The radiotherapy technician has the patient lie on the treatment table as in the simulator and adjusts the treatment field. Then, before operating the treatment machine, the technician leaves the room where the patient is and goes to the control room. The control room is a room right next to the treatment room, and the treatment room can be monitored from this room through television cameras. In addition, whenever the patient needs anything, their speech can be heard through a microphone system called an "Intercom." When necessary (when the patient feels uncomfortable or ill), the treatment can be stopped and the treatment team can enter the room. It is very important that the patient does not move during treatment. When the radiotherapy machine is operating, the radiation cannot be seen or heard, and you will probably not feel anything.

The radiation delivered in external radiation therapy does not spread or transfer to the patient's relatives or the environment. People receiving external radiotherapy pose no risk to their household, relatives or surroundings. However, in brachytherapy, where radioactive materials are placed inside the body, and in treatments with radioactive substances given by mouth or intravenously (systemic treatment), patients may emit radiation to their surroundings for a temporary period. During this time, patients are monitored in isolated, special hospital rooms, and they are advised to stay away from pregnant women and children under 18 for a few weeks.

The simultaneous administration of radiotherapy and chemotherapy is called chemoradiotherapy. In some types of cancer, using radiation therapy together with chemotherapy increases the effectiveness of treatment, and the tumor can be controlled better. Chemotherapy makes radiation more effective by increasing the sensitivity of cancer cells to radiation. Using chemotherapy and radiation therapy together may increase the likelihood of side effects. Therefore, patients receiving concurrent treatment should be checked at regular intervals.

Radiation therapy is given on an outpatient basis 5 days a week, excluding weekends. The total duration of treatment varies from 1 day to 7 weeks depending on the type of tumor, the type of treatment (curative/palliative), the radiotherapy dose and previously applied treatment approaches. The daily treatment time is usually 15-30 minutes.

Because radiation therapy also affects the normal cells around the cancer cells, it can cause some side effects depending on the area treated. There are two types of side effects in radiation therapy: acute and chronic. Acute or short-term side effects can occur after treatment begins and generally resolve completely a few weeks after treatment ends. Chronic or long-term side effects can develop months or years after treatment and can sometimes be permanent. The most common acute side effects are weakness, fatigue and loss of appetite, and these can occur in all individuals receiving radiation therapy regardless of the treatment area. Other side effects vary depending on the person, the area to which radiation is applied and the radiation dose. In general, in addition to skin changes, hair loss and difficulty swallowing may be seen in patients treated in the head and neck area; nausea, vomiting and diarrhea in patients treated in the abdominal area; and burning and bleeding in the urine or rectum in patients treated in the pelvic area. These side effects are often temporary and can largely be brought under control with various medications. Secondary cancers can rarely develop late as a result of radiotherapy.

Hair may fall out in patients who receive radiation to the brain and skull area. Hair loss may vary according to the radiation dose received and the size of the area treated. For example, complete hair loss is seen in people who receive radiation to the entire brain area, whereas partial hair loss is expected in those who receive radiation to only part of it. After treatment, hair often grows back within months. However, there may be changes in the quality, color and shape of the hair. In people who receive radiation to an area other than the region with scalp, there will be no hair loss due to radiation therapy.

During radiation therapy, great care must be taken of the skin in the treated area. The skin in the treated area becomes more sensitive than normal and can be injured very easily. Redness, irritation and darkening of the skin color, as if sun-tanned, may be seen. After a few weeks, the skin in the treatment area may become very dry, and itching and a feeling of discomfort may occur.

Deodorant, perfume, cologne, cosmetic products or any medication should not be applied to the skin in the treated area without consulting the doctor. The treated area should be cleaned with lukewarm water, and rubbing, scrubbing and using a washcloth or exfoliating mitt should be avoided. Because the skin in the treated area may be sensitive to temperature, hot or cold applications should not be made. Tight clothing should be avoided over the treatment area, and loose, cotton clothing should be preferred. If the treatment area needs to be shaved, you may use an electric shaver after consulting your doctor. Products such as razors, waxing, pre-shave lotion or hair-removal cream must absolutely not be used. The treated area should be protected from the sun, and, if possible, covered before going outside. To protect against the sun's rays, depending on the treated area, you may wear long-sleeved cotton clothing and a hat, and you may use products containing protection factors after consulting your doctor.

Marks are made on the bodies of patients receiving radiation therapy with special pens and marking tapes to define the treatment areas. The treatment technicians renew these marks regularly. It is very important to preserve these marks throughout the treatment. Marks that begin to blur or disappear should not be redrawn at home; the treatment technician and doctor should be informed. There is no harm in patients washing during treatment. However, to keep the marks from coming off, it is recommended not to use very hot water, exfoliating mitts or washcloths.

During radiation therapy, it is very important to eat adequately and in a balanced way and not to lose weight. So that normal cells can renew themselves, foods rich in calories and protein should be preferred (for example, meat, fish, chicken, cheese, yogurt and milk). Eating small amounts at frequent intervals will both allow more nutrients to be taken in and reduce digestive problems.

After radiation therapy is completed, follow-up visits are necessary after a certain time and at certain intervals so that the outcome of treatment and the side effects can be evaluated. Unless your doctor recommends otherwise, follow-up examinations are usually every three months in the first year, every six months in the following two to three years, and yearly thereafter. In addition to a physical examination, some blood tests and imaging tests may be requested at follow-up visits. Coming to follow-ups on time is very important for your health.