Radiation therapy is also known as beam therapy. It has been used for many years to treat cancer. Since that time, many developments have been made and great progress has been made in areas such as increasing effectiveness and keeping side effects at a minimum level. For better treatment results, evaluations are made by expert teams with a multidisciplinary approach.
There are many different forms of beam therapy.
- As a single treatment
- With systemic agents
- Before or after the operation (The aim is to keep the probability of finding a very small tumor at a minimal level)
- In order to relieve the patient’s complaints in advanced diseases
The treatment process may vary according to the general condition of the individual and the course of the disease. In addition, the dose for the patient, possible side effects and the characteristics of the treatment site should also be considered.
Protecting healthy cells and organs outside the area where the tumor is located is one of the important subjects of oncology. In certain types, such as laryngeal and breast cancer, instead of operations in which the entire organ is removed, the long-term results of individuals who are given only the tumor and some normal tissue nearby, and then adjuvant, that is, protective radiotherapy, are similar to each other. In addition, organ preserving procedures show much less side effects as expected.
How does radiotherapy work?
In radiotherapy, which is a treatment method that specifically targets a specific area, radiation energy is used to neutralize cancerous cells. Radiation therapy ionizes atoms and damages their DNA to kill tumor cells. This damage occurs by breaking the double helix of DNA. At this point, both normal cells and cancerous cells in the area where the treatment is applied are exposed to the ionizing effect of radiation. However, normal cells detect and repair DNA damage caused by radiation much faster. Cancerous cells, on the other hand, are in the center of proliferation and move much faster in growth, and therefore, detecting and repairing DNA damage is disadvantageous compared to normal cells. Normal tissues also have certain limits for their exposure to radiation. At this point, the balance of the applied radiation should be carefully adjusted. The division of the total dose of radiation into minimal daily levels (fraction) of the treatment process allows normal cells to repair themselves.
Radiotherapy techniques are examined as 3 main titles.
- External radiotherapy
- Brachytherapy (internal radiotherapy)
- Intraoperative (during the operation) radiotherapy
Among these methods, external radiotherapy is the most frequently applied. In this method, an external beam is used as a radiation source outside the patient.
Accelerating charged particles such as protons or electrons or cobalt 60 is used to produce ionizing radiation.
Linear accelerator: In this accelerator, electron particles are accelerated to reach a high energy to form x-rays, or photons. It can create photon or electron beams with different levels of energies, and the output of these particles is controlled by high-tech computers. Photons are used in cancers of internal organs, as they can reach tissues and cells further inside.
Electrons are generally used in diseases such as breast and skin cancer, that is, in superficial tumors. In this way, any damage to the internal organs can be prevented. In general, electron and photon particles can also be used in combination for optimal effect.
The term conformal therapy is used for the method of administering as minimally as possible to normal tissues and high doses to the area where cancerous cells are present. By using 3D Conformal RT (3D-CRT) together with computerized tomography and magnetic resonance imaging methods, the dose of radiation to be received by the tumor and surrounding tissues can be calculated separately. This way, side effects are kept as minimum. Apart from this, if necessary, in the future, radiation can be given to an area where the beam is delivered.
IMRT (Intensity Modulated Radiotherapy) allows the radiation beam from a single source to be applied at different intensities to different parts of the target area.
In the treatment of each individual case, real-time imaging allows for more effective determination of the target area. Under the heading of radiotherapy, these technologies are generally referred to as imaging-guided radiotherapy (IGRT).
RapidArc, which stands for Volumetric Intensity Modulated Arc Therapy (VMAT), is an irradiation method that can rapidly apply intensity modulated radiotherapy under the guidance of imaging methods.
Due to the specific properties of heavy particles, it allows a more sensitive radiotherapy for the tumor area and less damage to normal tissues is ensured. This movement of the proton, which releases its energy sharply when it reaches the target tissue, is called the Bragg peak. It is thought to have fewer side effects than different methods.
Whether protons have an advantage over photons in many types of cancer is the subject of research, but some childhood cancer diseases, uveal melanoma, etc. No superiority has been detected yet, except for diseases. The results of proton therapy, especially intensively applied in prostate cancer, stand out as equivalent to 3-dimensional conformal methods.
Stereotactic radiotherapy techniques
It is the process of making the total dose calculated for the treatment once or several times. These techniques are examined in two main groups as SBRT and radiosurgical SRS. Stereotactic radiosurgery (SRS) is generally applied to brain tumors, while stereotactic body radiotherapy (SBRT) is generally applied to organs other than the brain such as liver, lung, and spine.
It is a part of the treatment to prepare the individual for the transfer of hematopoietic cells in lymphoma and leukemia diseases. This method has two purposes. The first is to clear cancerous cells as much as possible, and the other is to suppress the immune system, namely immunosuppression, to prevent the rejection of stem cells by the body.
Do not let “radiosurgery” scare anyone; It is not a penetrating operation. We call it radiosurgery because very high doses are given at once and eliminate the tumor. The patient does not feel any pain. Instead of waiting for a response for months after a treatment that lasts for weeks, we can get results in a relatively short time, by completing the procedure in a short time.
In stereotaxic radiosurgery, beams are directed to the target volume from multiple different angles. While high doses are applied in the coincidence area of the beams, the surrounding normal tissues are best preserved. Initially, it is applied to tumors under 3 cm. It has also become applicable to nearby tumors. For malignant tumors, the process that is initially tried to be completed in one session as much as possible; It was increased to three sessions when it was understood that radiotherapy also has an immunological effect and that this occurs mostly with fractionated radiosurgery…
Radiosurgery was previously applied to tumors that were located around critical organs or in areas that were difficult to surgically remove. Studies published over time have shown that it gives results on par with surgery in many localizations, and this easy method has been successfully applied to more and more patients. In the current process, it’s not just the brain; It can be easily applied to almost any tumor in any part of the body, especially in the lung, prostate, pancreas and liver.
Results of Radiosurgery
Although the results of radiosurgery are mostly the same as surgery, it is a very simple application for the patient; there will be no pain. The process ends with the patient lying on the treatment device for about half an hour without moving. In the treatment of organs in the chest or abdomen, such as the lungs, the patient should hold their breath at certain intervals. While this allows us to better focus on the tumor, it also reduces the margins of safety we give to avoid missing the displaced tumor during breathing. Therefore, while the accuracy of our work increases, the damage we can do to normal tissue becomes minimal.
Unlike other surgical or chemotherapy processes, radiosurgery does not suppress the immune system. Recent studies show us that radiotherapy, and especially radiosurgery, activates the immune system. Released cytokines and activated pathways mediate this effect.
When you are diagnosed, before starting the treatment, take the opinion of each of the radiation oncology, medical oncology and surgery doctors, and decide on the treatments to be applied by listening to all three. Radio surgery applications, which started with Gamaknife in the 1960s, began to be applied in linear accelerators after the 1980s. Because it starts with Gamaknife; Although there is a perception that radiosurgery is performed only with Gamaknife, similar dose distributions can be applied efficiently in devices such as linac-based, cyberknife or tomotherapy.
Brachytherapy (internal radiotherapy)
In this method, the radiation source is located close to or within the treatment area. It is especially used in gynecological diseases such as cervix and prostate cancer.
Intraoperative (during surgery) radiotherapy (IORT)
It is the process of giving radiation during the operation. This method is performed as a single session during the surgery. If the chance of recurrence of cancerous cells is high, radiotherapy can be applied during surgery. The application area of this method is cancer types that usually occur in the abdominal and inguinal area, head and neck cancers and breast cancer. If an effective control is not achieved in intraoperative radiotherapy applied as a single dose, this treatment is supported with external radiotherapy.
Possible side effects of radiotherapy
Side effects that individuals show generally depend on the area being treated and the characteristics of the disease. However, the total dose is also related to factors such as the amount of dose in each fraction and the sensitivity of the individual’s cells to radiotherapy. In addition, other types of treatment that the patient receives are also an effective factor at this point. Usually, the tissues may swell during radiotherapy. Edema formation is seen. Vomiting and nausea may occur with radiation applied to the abdominal area. In the treatment applied to the head and neck area, sores may occur in the throat and mouth. In the treatment of the thorax, inflammation may occur in the esophagus. These events can cause difficulty in swallowing, namely dysphagia and dehydration. Radiotherapy to the lower abdomen may cause some problems in the urinary tract and intestines. The edema decreases after the treatment process and the side effects disappear.
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