Metastatic brain tumors are much more common than primary brain tumors, occurring in 10 to 30 percent of all adult cancers. Left untreated, many patients die not from their primary cancer but from progression of the brain tumor. In the past, some stereotactic radiosurgery systems were limited in the number of metastases that could be treated and had significant difficulty in reaching widely spaced lesions in the brain.
Mayo Clinic's updated stereotactic radiosurgery system can treat many brain metastases, including widely situated tumors, often in a single 90-minute session. "With our old unit, we would rarely treat more than six metastases, and it was very complicated if a patient had lesions at opposite ends of the brain. The stereotactic head frame had to be removed and repositioned, and the patient rescanned, to reach those targets," says Michael J. Link, M.D., a neurosurgeon at Mayo Clinic in Rochester, Minn. "The new system has eliminated those problems. For cases that were considered somewhat hopeless, we have something new to offer."
Whole-brain radiation usually requires 10 to 15 treatments over a period of two to three weeks. Concern about long-term cognitive impairment may result in lower radiation doses, which can diminish tumor control. If new lesions develop, physicians may be reluctant to repeat whole-brain radiation. In addition to treating multiple lesions in a single session, stereotactic radiosurgery doesn't cause hair loss and can be used later to treat new lesions.
Among patients who can particularly benefit from stereotactic radiosurgery are young women with breast cancer that metastasizes to the brain. "These patients are going to be long-term breast cancer survivors, so we don't want to give them whole-brain radiation," Dr. Link says.
Mayo is participating in an ongoing National Cancer Institute-Radiation Therapy Oncology Group study comparing treatment with stereotactic radiosurgery plus whole-brain radiotherapy to treatment with stereotactic radiosurgery alone, in patients with one to three brain metastases. "Our hope is that the results will show sufficient tumor control from stereotactic radiosurgery that whole-brain radiotherapy can be avoided," Dr. Link says.