(SRS) combines the principles of stereotaxy, or 3-D target localization, with
multiple cross-fired beams from a high-energy radiation source to precisely
irradiate an abnormal (often times cancerous) lesion within a patient's body.
This technique allows maximally aggressive dosing of the target, while normal
surrounding tissue receives lower, non-injurious doses of radiation. The ideal
objective is the ablation or destruction of the targeted area without damaging
any normal tissue outside of the defined target area.
differs from conventional radiotherapy in several ways. The efficacy of
radiotherapy depends primarily on the greater sensitivity of tumor cells to
radiation relative to normal tissue. With all forms of standard radiotherapy,
the spatial accuracy with
which the treatment is focused on the tumor is a secondary concern; normal
tissues are protected by administering the radiation dose over multiple sessions
(fractions) daily for a period of a few to several weeks.
In contrast, radiosurgery, by its very definition, requires much greater
targeting accuracy. With SRS,
normal tissues are protected by both selectively targeting only the abnormal
lesion, and using cross-firing techniques to minimize the exposure of the
adjacent anatomy. Since highly destructive doses of radiation are used, any
normal structures (such as nerves or sensitive areas of the brain) within the
targeted volume are subject to damage as well.
Typically, SRS is administered in one to five daily fractions over consecutive
days. Nearly all SRS is given on an outpatient basis without the need for
anesthesia. Treatment is usually well tolerated, and only very rarely interferes
with a patient's quality of life.
has been used for more than 30 years to treat
benign and malignant
tumors, vascular malformations, and other disorders of the brain with minimal
invasiveness. To date, more than 200,000 patients have been treated worldwide
with radiosurgery. The success of SRS is based, to a large extent, on the use of
a multidisciplinary approach, which requires close interaction between surgeons,
radiation oncologists, medical oncologists, physicists, diagnostic radiologists,
technicians, and nurses. This specialized team is responsible for the selection
of appropriate patients for SRS, treatment delivery, and long-term follow-up.