Stereotactic Radiosurgery
Stereotactic radiosurgery (SRS) treats brain disorders with a precise delivery of a single, high dose of radiation in a one-day session. Focused radiation beams are delivered to a specific area of the brain to treat abnormalities, tumors or functional disorders.
Body radiosurgery is rare. Only a few Centers of Excellence are able to immobilize and treat the body in a radiosurgical fashion, using high-level special technology.
Fractionated stereotactic radiation treatments-which are received over a period of days or weeks-may be administered to the body with the assistance of removable masks and frames that achieve a lesser degree of immobilization. Stereotactic radiosurgery is limited to the head and neck, because these areas can be immobilized with skeletal fixation devices that completely restrict the head's movement, permitting the most precise and accurate treatment. One-session treatment without a skeletal fixation device is not recommended because of the high potential for damage to healthy brain tissue, cranial nerves (optic, hearing, etc.) and the brain stem.
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.
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.Side effects include the following:
- Swelling: As with all radiation treatments, the cells of the irradiated tumors lose their ability to regulate fluids, and edema or swelling may occur. This does not happen in all treatments. If swelling does occur, and it causes symptoms that are unpleasant, then a mild course of steroid medication may be given to reduce the fluid within the tumor cavity
- Necrosis: The tumor tissue that remains after the radiation treatment will typically shrink. On rare occasions this necrotic or dead tissue can cause further problems and may require removal. This occurs in a very small percentage of cases
- Other Effects: Other side effects may occur dependent upon the target site and the dose of radiation received. This should be discussed throughly with your treating physician. For more information on side effects and radiation injury Click Here
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.
Stereotactic radiosurgery can be used in patients who have failed standard radiation techniques, or in patients who have already received whole brain radiation or the maximum radiation dose permissible. There is little literature on radiation-induced new tumors caused by stereotactic radiosurgery. It is expected that the possibility of developing a tumor is 1 in 10,000 cases. This may be attributed to the precision of the treatment and the sparing of healthy nerves and tissues. A patient who has had stereotactic radiosurgery for a brain tumor or another condition may have open skull surgery later without problems. In many cases, stereotactic radiosurgery can be performed again if necessary.
