Nisbetiye Mah. Yücel Sok. No:6
34340 1. Levent, Beşiktaş, İstanbul
Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT)
Stereotactic radiosurgery (SRS) is a non-surgical radiation treatment which is applied in order to eliminate functional anomalies and small tumors in brain. In the session of a high dose treatment, which is fewer in number in comparison to the traditional treatment, it can help the preservation of the healthy tissue by sending the radiation precisely directed to target. SRS applied for treating the body tumors is called stereotactic body radiotherapy (SBRT).
SRS and SBRT are mostly applied in outpatient settings. Consult your physician about whether you need to plan to be taken back to home by one of your relatives after the treatment and whether you need to avoid eating, drinking or taking medicine a few hours prior to the treatment. If you have a suspect of pregnancy or are breast feeding or taking oral medicine or insulin to keep your diabetes under control, inform your physician about this. Talk with your doctor whether you have a medical device, implanted into your body, claustrophobia or allergy against contrast agents.
What is stereotactic radiosurgery and how it is used?
Stereotactic radiosurgery (SRS) is an extremely delicate form of a radiation treatment, which has been originally developed to treat functional anomalies and small tumors developing in brain. The principles of cranial SRS, which allows sending radiation rays with one or two millimeters of accuracy and is named high precision radiation, are used in the treatment of body tumors with an operation, named stereotactic body radiotherapy (SBRT).
Regardless of its name, is not a surgical procedure and applies the precisely directed radiation in one or few treatment sessions on the target at higher doses in comparison to the traditional radiation treatment. Thanks to the development of the highly advanced radiation technologies, which allows sending maximum doses to the targeted area, while minimizing the doses sent to the healthy tissues around, it has become possible to use this treatment. The purpose is to destroy the tumor and to apply the doses that will provide permanent local control.
SRS and SBRT is based on various technologies:
- Three-dimensional imaging and localization techniques which can determine the precise coordinates of a target in vitro
- The system which keep the patient motionless and carefully locate and sustain patient’s position.
- Gamma or X ray bundles concentrating on tumor or anomalies at high level
- Image-guided radiation therapy (IGRT) uses the medical imaging to confirm the location of a tumor just before the application of radiation and during sending radiation in some cases. It increases the precision and accuracy of the IGRT treatment.
The three-dimensional imaging like CT, MRI and PET/CT is used to determine the location and certain size and shape of an in vitro tumor. These images also guide the combination of radiation bundles from different angles and planes and the planning of treatment, tailored for careful positioning of the patient during treatment sessions.
Whereas SRS represents the daily treatment widely, the physicians sometimes advice multiple stereotactic treatment sessions. As it is necessary to take the surrounding normal tissue, exposed to high dose of single radiation, into consideration and to limit the reaching dose, and the volume of normal tissue, receiving a treatment dose, increases in parallel with the tumor’s size; this approach is important for the tumors, with more than 2,5 cm diameter. Sending radiation in several sessions, instead of a single session, can improve the safety and allow improving the recovery of normal tissue between treatment sessions. For this reason, while the division of treatment into fractions allows sending high doses, it allows sustaining an acceptable safety profile. This operation is mostly named as fractional stereotactic radiotherapy (SRT) and means giving the typically focused radiation between two and five sessions.
SRS and SBRT are significant alternatives of invasive surgery for the patients which are not available to be taken into an operation and the tumors and anomalies which carry the following traits:
- Difficult to access
- Close to vital organs/anatomic areas
- Movable areas inside body
SRS is used to treat the following:
- Many kinds of brain tumor which includes the following:
- benign and malign
- primary and metastatic
- Single and more than one
- Postoperative residual tumor cells
- Intracranial, orbital and skull base tumors
Arteriovenous malformations (AVMs), enlarged clue-shaped blood veins, which impair the normal blood flow and sometimes bleed.
Trigeminal neuralgia (facial nerve disorder), tremor and other similar neurological disorders
Today, SBRT is used in benign and malignant small and medium sized in vitro tumors and in the treatment of the common diseased areas, including the following, and/or its use is studied:
- head and neck
Essentially, SRS operates in the same way with other radiation treatment types. It harms the DNA of tumor cells without actually moving the tumor away. As the result, these cells lose their reproduction capacities. After the treatment, benign tumors generally decrease in size in the period between 18 months and two years. Malign and metastatic tumors can decrease in size faster, even in few months. When arteriovenous malformations (AVMs) are treated with SRS, they can slowly begin thickening and closing in the period of few months after treatment. Many tumors will stay stable and inactive without any change. As the purpose is to prevent the tumor from enlarging, it is thought to be a success. Due to the inflammatory response, which becomes stable inside the tumor tissue for some tumors over time, like acoustic neuroma, a temporary enlargement can be witnessed or the subsequent tumor recession, named pseudo-regression, is observed.