Radiosurgery (one-session treatment) has such a dramatic effect in the target zone that the changes are considered "surgical." Through the use of three-dimensional computer-aided planning and the high degree of immobilization, the treatment can minimize the amount of radiation that passes through healthy brain tissue. Stereotactic radiosurgery is routinely used to treat brain tumors and lesions. It may be the primary treatment, used when a tumor is inaccessible by surgical means; or as a boost or adjunct to other treatments for a recurring or malignant tumor. In some cases, it may be inappropriate.
How it Works:
Stereotactic radiosurgery works the same as all other forms of radiation treatment. It does not remove the tumor or lesion, but it distorts the DNA of the tumor cells. The cells then lose their ability to reproduce and retain fluids. The tumor reduction occurs at the rate of normal growth for the specific tumor cell. In lesions such as AVMs (a tangle of blood vessels in the brain), radiosurgery causes the blood vessels to thicken and close off. The shrinking of a tumor or closing off of a vessel occurs over a period of time. For benign tumors and vessels, this will usually be 18 months to two years. For malignant or metastatic tumors, results may be seen in a few months, because these cells are very fast-growing.
Is it Appropriate?:
Because all forms of radiation treatments work over time, they may be inappropriate if symptoms are severe or life-threatening. Relief of acute symptoms may drive the first treatment choice to open skull surgery or medication. For instance, if the symptoms at the time of diagnosis are so severe that quality of life is affected, the appropriate choice for the first treatment may be surgery to relieve those symptoms. The secondary treatment could then be radiosurgery.
In other cases where cells are extremely fast growing (with or without severe symptoms), such as in brain metastases, radiosurgery can quickly control the brain tumors to allow time to treat the primary cancer site. Medication can be given for the side effects (such as edema), and radiation therapy may be used over a period of time to help eliminate any stray cancer cells from the brain.
Source: IRSA Radiosurgery Overview