Case study published in The Lancet documents development of malignant tumor 7 years after radiosurgery to treat benign tumor

November 25, 2000

FINDING:
Seven years after undergoing radiosurgery to treat a benign tumor, a 70-year-old woman developed a malignant brain tumor called a glioblastoma, according to a case report prepared by researchers at Cedars-Sinai's Maxine Dunitz Neurosurgical Institute. It is published in the November 2000 issue of the British medical journal, The Lancet.

BACKGROUND:
The patient first complained of transient dizziness followed by a headache. Evaluation found no evidence of neurologic deficit. According to a follow-up MRI performed six years later, the tumor, located near the superior saggital sinus, was growing. Therefore, it was treated with stereotactic radiosurgery, a procedure that focuses radiation from numerous angles, bombarding the tumor while minimizing exposure to surrounding tissue. All of these early diagnostic and treatment measures were performed at institutions other than Cedars-Sinai.

Within two months of treatment, the patient experienced partial blindness resulting from swelling of tissue around the tumor. Although this edema was treated with high-dose steroids, it worsened and the patient gradually developed complications from the steroids. Two years after radiosurgery, neurosurgeons surgically removed as much of the lesion as possible. During the operation, the surgeons noted that adjacent brain tissue showed evidence of damage caused by radiation.

The patient's visual field improved and she exhibited no neurologic deficit following surgery. MRI scans showed improved edema and no evidence of tumor progression. However, seven years after the original radiosurgery, the patient again experienced visual disturbance as well as short- and long-term memory impairment. An MRI revealed a new lesion in the radiation field, and this tumor was surgically removed by Dr. Black and Dr. Yu at the Maxine Dunitz Neurosurgical Institute. It was found to be a glioblastoma multiforme, a type of malignancy that is extremely difficult to treat.

RAMIFICATIONS:
Previous reports in the medical literature have shown that the use of external beam radiation to treat a variety of conditions can induce development of glioblastoma. But radiosurgery - which has been available for about 30 years - is intended to reduce such risk by exposing surrounding tissues to only minimal doses of radiation.

According to the Lancet article, "This radiosurgery-induced malignancy may portend further reports of tumour induction. The theoretical risk of tumour induction by low doses of radiation to normal neural tissue after radiosurgery is now confirmed. Reports of additional cases of radiosurgery-induced tumours might temper the use of this increasingly used technique for benign surgically accessible lesions."

"In no way would we suggest that a patient avoid radiosurgery when prescribed by a physician. We submitted this unique case report to inform physicians and surgeons of this rare possibility and to encourage further study and awareness. But the risk of a patient developing a glioblastoma after treatment with radiosurgery appears to be extremely small," said John S. Yu, M.D., neurosurgeon and the article's first author.
-end-
INVESTIGATORS:
John S. Yu, M.D., neurosurgeon; Dean Wilson, certified physician assistant; Keith L. Black, M.D., neurosurgeon, MDNSI director (Cedars-Sinai Maxine Dunitz Neurosurgical Institute and Department of Neurosurgery at the University of California, Irvine). William H. Yong, M.D. (Department of Pathology at Cedars-Sinai Medical Center).

MEDIA CONTACT:
For media interviews and additional information, please contact Sandra Van via e-mail: sandy@vancommunications.com or by telephone at 1.800.396.1002.

Cedars-Sinai Medical Center

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