Stereotactic radiosurgery (SRS) is a kind of external-beam radiation therapy capable of precisely targeting small areas within the body. Although its name would suggest that SRS is an invasive procedure, there is actually no cutting involved. Initially developed for use on tumors and lesions in the brain, SRS is now sometimes used to shrink or slow the growth of tumors in other parts of the body, when it is referred to as stereotactic body radiotherapy (SBRT).
Generally, patients undergoing SRS are asked not to eat anything after midnight on the day of the procedure. If the brain is being treated, hair creams or hairspray should not be used the day before. During treatment, the patient is positioned lying down on a table. The table then slides into a machine that delivers the radiation. Three types of machines may be used in SRS treatment: a Gamma Knife® unit, a linear accelerator and a cyclotron.
When the SRS procedure begins, three-dimensional imaging, such as a CT, MRI or PET/CT scan, is used to locate the abnormality and determine its shape and size. In some cases, a contrast agent will be administered to the patient to make the tumor more visible. A precise high dose of radiation is then aimed at the tumor area, making it essential that the patient remain extremely still. A head frame or individual body mold designed to limit a patient’s movements may be required. Up to five separate sessions, each between 30 minutes and one hour in duration, may be necessary for complete treatment.
In spite of the careful precision with which stereotactic radiosurgery is administered, there may be damage to surrounding healthy tissue. In patients who are treated for brain tumors, swelling of the brain, or brain edema, may occur. Although this symptom may resolve on its own, in some cases medication may be required. Other serious complications may include seizural activity following treatment, a possible regrowth of the targeted tumor or a development of a secondary cancer. More common side effects of SRS treatment may include:
- Redness, blistering or peeling of skin
- Hair loss at the site
- Nausea and vomiting
- Difficulty swallowing