Radiosurgery Q and A
What is stereotactic radiosurgery?
Stereotactic radiosurgery (also called SRS) is a means of treating 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. Stereotactic radiosurgery is limited to the head and neck, because these areas can be immobilized with a device that completely restricts the head's movement, permitting the most precise and accurate treatment. One-session treatment without a head immobilization device is not usually recommended because of the high potential for damage to healthy brain tissue, cranial nerves (optic, hearing, etc.) and the brain stem.
Why is it called surgery?
Radiosurgery (a one-session treatment) has such a dramatic effect in the targeted treatment area that the changes are considered "surgical." Through the use of three-dimensional computer-aided planning devices and the high degree of head 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 an adjunct to other treatments for a recurring or malignant tumor. In some cases, it may be an inappropriate treatment option.
How does stereotactic radiosurgery work?
Stereotactic radiosurgery is based on the same principles as other forms of radiation treatment. It does not remove the tumor or lesion, but the radiation beams distort 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, because these cells are very fast-growing, results may be seen in a few months.
What are the side effects?
- Swelling: As with all radiation treatments, the tumor cells 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 thoroughly with your physician.
Is radiation treatment right for me?
Because all forms of radiation treatments work over time, this course of treatment may be inappropriate if symptoms are severe or life-threatening. For example, if relief of acute symptoms is urgent, the first treatment choice may be traditional open skull surgery or medication to relieve symptoms affecting quality of life. Secondary treatment may 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 stray cancer cells from the brain.
What if I had previous radiation treatments?
Stereotactic radiosurgery can be used in patients where standard radiation techniques have failed, or in patients where the maximum radiation dose permissible has been administered. 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.
What are the types of radiosurgery?
There are three basic forms of stereotactic radiosurgery represented by three different technological instruments. Each instrument operates differently, has a different source of radiation and may be more effective under different circumstances.
- Cobalt-60 based (photon)
- Linear accelerator based (linac)
- Particle beam (proton)
Am I a candidate for radiosurgery?
Stereotactic radiosurgery may or may not be appropriate for a condition. It may be used as the primary treatment or recommended in addition to other treatments that are needed. The members of the multi-disciplinary radiosurgery treatment team make the determination as to whether or not someone can be treated.