The use of stereotactic radiosurgery has less risk of injuring the cranial nerves where these tumors, non-vestibular schwannomas, appear. Schwannomas are typically benign tumors arising from the covering of nerves.
The study reviewing patient outcomes after radiosurgery appears in a recent issue of the International Journal of Radiation Oncology, Biology, Physics.
Stereotactic radiosurgery is a radiation therapy technique that uses a large number of narrow, precisely aimed, highly focused beams of ionizing radiation. The beams are aimed from many directions circling the head and meet at a specific point.
"Nonvestibular schwannomas are quite rare, representing less than one-half of one percent of intracranial tumors," said Bruce Pollock, M.D., a Mayo Clinic neurosurgeon and the lead author of the study. "Our study found that radiosurgery offers patients an alternative to surgical resection that has less risk of injuring the cranial nerves."
The study followed 23 patients who had radiosurgery for nonvestibular schwannomas at Mayo Clinc from April 1992 to February 2000. Nine of the study’s patients had undergone one or more prior tumor resections or surgeries. One patient had a malignant schwannoma.
After radiosurgery, 22 of 23 tumors (96 percent) were either smaller (12) or unchanged in size (10). In the study, one patient with a malignant schwannoma had tumor progression outside the irradiated volume despite having both radiosurgery and fractionated radiation therapy; he died four years later. No patient with a lower cranial nerve schwannoma developed any hearing loss, facial weakness, or swallowing difficulty after radiosurgery.
In the study, Dr. Pollock and his colleagues concluded that although the reported number of patients having radiosurgery for nonvestibular schwannomas is limited, the high tumor control rates demonstrated after vestibular schwannoma radiosurgery should apply to these rare tumors. Compared to historical controls treated with surgical resection, radiosurgery appears to have less treatment-associated death for nonvestibular schwannomas, especially for schwannomas involving the lower cranial nerves.
Contact:
Lisa Copeland
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e-mail: newsbureau@mayo.edu