SRS - What is Stereotactic Radiosurgery

Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) is a highly precise form of radiation therapy to targets in the brain where delivery is accurate to within one millimeter.  SRS is a non-surgical treatment that delivers precisely-targeted radiation at much higher doses, in only a single or few treatments, as compared to traditional radiation therapy. This treatment is only possible due to the development of highly advanced radiation technologies that permit maximum dose delivery within the target while minimizing dose to the surrounding healthy tissue. The goal is to deliver doses that will destroy the tumor and achieve permanent local control.  SRS rely on several technologies: (1) three-dimensional imaging and localization techniques that determine the exact coordinates of the target within the body (CT, MRI, PET scan); (2)  systems to immobilize and carefully position the patient and maintain the patient position during therapy; (3) highly focused gamma-ray or x-ray beams that converge on a tumor or abnormality; (4)  image-guided radiation therapy (IGRT) which uses medical imaging to confirm the location of a tumor immediately before, and in some cases, during the delivery of radiation.

SRS Treats Brain Tumors

SRS is used to treat many types of brain tumors including: benign and malignant, primary and metastatic, single or multiple, residual tumor cells following surgery, intracranial, orbital and base-of-skull tumors, arteriovenous malformation (AVMs, a tangle of expanded blood vessels that disrupts normal blood flow in the brain and sometimes bleeds), other neurological conditions like trigeminal neuralgia (a nerve disorder in the face), tremor, etc. SRS can be delivered usually as one treatment, or sometime two or up to five daily treatments. SRS fundamentally works in the same way as other forms of radiation treatment. It does not actually remove the tumor; rather, it damages the DNA of tumor cells. As a result, these cells lose their ability to reproduce. Following treatment, benign tumors usually shrink over a period of 18 months to two years. Malignant and metastatic tumors may shrink more rapidly, even within a couple of months. When treated with SRS, arteriovenous malformations (AVMs) may begin to thicken and close off slowly over a period of several years following treatment. Many tumors will remain stable and inactive without any change. Since the aim is to prevent tumor growth, this is considered a success. In some tumors, like acoustic neuromas, a temporary enlargement may be observed following SRS due to an inflammatory response within the tumor tissue that overtime either stabilizes, or a subsequent tumor regression is observed called pseudoprogression.

(REFERENCE. RadiologyInfo.org from ACR and RSNA)