Radiation Oncology

Radiation oncology is a medical specialty that focuses on the therapeutic use of ionizing radiation in cancer treatment. This treatment method, also known as radiotherapy, constitutes one of the three main pillars of oncological treatment, alongside surgery and chemotherapy. It is known that approximately half of all cancer patients require radiotherapy at some point during their treatment process. The Koru Hospital Department of Radiation Oncology offers the most effective and safe treatment options to cancer patients with its high-technology radiotherapy systems and experienced specialist staff.

What is Radiotherapy and How Does It Work?

Radiotherapy is based on the principle that high-energy ionizing radiation damages the DNA structure of cancer cells, thereby eliminating their ability to proliferate and divide. Since the DNA repair mechanisms of normal cells function more effectively compared to cancer cells, radiotherapy allows for the selective destruction of cancer cells while protecting healthy tissues. This fundamental biological difference forms the basis of the therapeutic potential of radiotherapy.

Radiation causes damage to cellular DNA through direct or indirect pathways. The direct effect occurs when radiation strikes the DNA molecule, causing double-strand breaks. The indirect effect is the damage caused to DNA by free oxygen radicals formed as a result of the radiolysis of water. As a result of these mechanisms, cancer cells become unable to divide and undergo programmed cell death (apoptosis). To increase the effectiveness of the treatment and reduce side effects, the total radiation dose is divided into small daily doses called fractions.

The Role of Radiotherapy in Cancer Treatment

Radiotherapy is used for different purposes in cancer treatment. These purposes are determined based on the stage of the disease, the localization of the tumor, the histological type, and the patient's general condition. The goal of the treatment can range from the complete eradication of the disease to the alleviation of symptoms.

• Curative radiotherapy: Administered alone or in combination with chemotherapy with the aim of completely destroying the tumor. Nasopharyngeal cancer, cervical cancer, and early-stage laryngeal cancer are among the tumor types where curative radiotherapy is successful.
• Adjuvant radiotherapy: Administered after surgery to reduce the risk of recurrence. It is frequently used in breast cancer, rectal cancer, and brain tumors.
• Neoadjuvant radiotherapy: Administered before surgery to shrink the tumor size and facilitate the operation. It is a common approach in rectal cancer and esophageal cancer.
• Palliative radiotherapy: Administered in advanced-stage cancers to alleviate symptoms such as pain control, stopping bleeding, and relieving obstructions.
• Prophylactic radiotherapy: Administered to control microscopic disease, particularly as cranial prophylaxis in small-cell lung cancer.

External Radiotherapy Techniques

External radiotherapy is applied by directing radiation from outside the body to the tumor area via devices called linear accelerators (LINAC). Modern linear accelerators produce high-precision radiation beams to target the tumor while maximizing the protection of surrounding healthy tissues.

Three-dimensional conformal radiotherapy (3D-CRT) is a technique where radiation fields are shaped based on three-dimensional imaging of the tumor. Intensity-modulated radiotherapy (IMRT) allows the intensity of radiation beams to be adjusted at different levels in different areas, enabling a more homogeneous dose distribution. This technique provides a great advantage, especially in head and neck tumors and prostate cancer, in protecting critical organs such as salivary glands, the rectum, and the bladder.

Volumetric modulated arc therapy (VMAT), as an advanced form of IMRT, significantly shortens treatment time. In this technique, the device rotates around the patient while simultaneously performing radiation beam shaping and intensity modulation. Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) are advanced techniques that allow high-dose radiation to be applied in a small number of fractions with millimeter precision.

Stereotactic Radiosurgery and Radiotherapy

Stereotactic radiosurgery (SRS) is a method used in the treatment of brain tumors and brain metastases, where a high dose of radiation is applied with millimeter precision in a single session or a very small number of sessions. Although no surgical knife is used, it is called "radiosurgery" because it provides a treatment efficacy equivalent to surgical intervention. Acoustic neuroma, meningioma, arteriovenous malformation, and brain metastases are the primary indications for SRS.

Stereotactic body radiotherapy (SBRT) allows for the application of high-dose radiation to tumors in organs outside the brain in a few sessions. Early-stage lung cancer, liver metastases, pancreatic cancer, and oligometastatic disease are common areas of SBRT application. Thanks to real-time imaging and motion tracking systems, physiological movements such as respiratory motion are compensated, increasing the precision of the treatment.

Internal (Brachytherapy) Radiotherapy

Brachytherapy is a radiotherapy method in which a radioactive source is placed directly into or near the tumor. Since this technique allows radiation to be delivered from a very close distance to the tumor tissue, a high dose is achieved in the tumor while the dose drops rapidly in the surrounding tissues. This feature makes brachytherapy an extremely effective treatment option, especially for certain tumor types.

Cervical cancer, endometrial cancer, prostate cancer, breast cancer, and head and neck tumors are the most common types of cancer where brachytherapy is applied. Intracavitary brachytherapy (application within a cavity), interstitial brachytherapy (application within tissue), and intraluminal brachytherapy (application within a lumen) describe different placement techniques. High-dose-rate (HDR) brachytherapy is currently the most widely used brachytherapy method, offering short treatment times and the convenience of outpatient application.

Treatment Planning Process

Radiotherapy treatment planning is a comprehensive and systematic process that extends from the patient's diagnosis to the completion of treatment. This process is carried out by a multidisciplinary team consisting of a radiation oncologist, a medical physicist, and a radiotherapy technician. Every stage of treatment planning directly affects the effectiveness and safety of the treatment.

In the simulation phase, the patient is immobilized in the treatment position using immobilization devices, and a computed tomography scan is performed. On the obtained images, the radiation oncologist defines the target volumes and critical organs. The gross tumor volume (GTV), clinical target volume (CTV), and planning target volume (PTV) are determined according to international standards. The medical physicist creates the optimal treatment plan in accordance with the defined volumes and dose constraints. After the plan is approved by the radiation oncologist, it is put into practice after passing through verification processes.

Image-Guided Radiotherapy

Image-guided radiotherapy (IGRT) is an advanced radiotherapy approach that ensures the verification of the patient's and tumor's position by performing imaging before each treatment session. Cone-beam computed tomography (CBCT), portal imaging, and optical surface monitoring systems are the primary imaging methods used in IGRT.

IGRT increases the accuracy of treatment, especially in lung, liver, and prostate cancers where tumor motion is significant. Thanks to daily position corrections, planning margins can be reduced, which means a reduction in the dose delivered to healthy tissues. Adaptive radiotherapy (ART) is the most current approach that allows the treatment plan to be re-optimized according to changes in tumor size or patient anatomy during the treatment process.

Side Effects of Radiotherapy and Their Management

The side effects of radiotherapy vary depending on the treated area, the dose applied, and the patient's individual characteristics. While acute side effects appear during or shortly after treatment, late side effects can develop months or years after treatment. With modern radiotherapy techniques, the frequency and severity of side effects have decreased significantly compared to the past.

In radiotherapy applied to the head and neck region, mucositis (mouth sores), xerostomia (dry mouth), dysphagia (difficulty swallowing), and dermatitis are common side effects. Esophagitis and pneumonitis can develop in treatment applied to the chest region; enteritis, proctitis, and cystitis can develop in treatment applied to the abdomen and pelvis region. Preventive measures, symptomatic treatments, and nutritional support play an important role in the management of these side effects.

Fatigue is the most common general side effect of radiotherapy and is seen in the vast majority of patients. Mild exercise programs, sleep hygiene, and dietary adjustments are effective approaches to coping with fatigue. Dermatological side effects manifest as redness, dryness, and peeling of the skin in the treated area.

Special Patient Groups and Approaches

Pediatric radiotherapy requires a specialized approach due to the potential effects of radiation on growth and development in children. Preferring advanced techniques such as proton therapy in children provides significant advantages in protecting healthy tissues. In elderly patients, hypofractionated (high dose in a small number of sessions) treatment protocols can be applied by taking into account accompanying diseases and performance status.

Re-irradiation is an approach that comes to the agenda in the treatment of recurrent tumors in an area that has previously received radiotherapy and requires careful planning. Observing cumulative tissue tolerance and minimizing normal tissue damage with modern treatment techniques are the basic conditions for performing this application safely.

Multidisciplinary Oncological Approach

The best results in cancer treatment are achieved through multidisciplinary teamwork. Tumor boards, where the radiation oncologist, medical oncologist, surgeon, pathologist, radiologist, nuclear medicine specialist, and supportive care team work together, play a central role in determining the treatment strategy for each patient. Treatment decisions are made within the framework of current guidelines and evidence-based medicine principles, taking into account the patient's individual characteristics.

Radiotherapy is frequently applied in combination with chemotherapy. Concurrent chemoradiotherapy provides superior results in certain types of cancer compared to the application of either treatment alone. Concurrent chemoradiotherapy is accepted as the standard treatment approach in cervical cancer, head and neck cancers, lung cancer, and rectal cancer. The combination of radiotherapy with new-generation systemic treatments such as immunotherapy and targeted therapies constitutes the focus of current research.

In the Koru Hospital Radiation Oncology department, our specialist physicians offer the most effective, safe, and individualized treatment services to cancer patients with high-technology radiotherapy devices and a multidisciplinary team approach. Each patient's treatment plan is evaluated by the tumor board, and an optimal treatment strategy based on current scientific data is determined.