"Stereotactic radiosurgery using the gamma knife provided high rates of tumor growth control, often with tumor regression, and low morbidity rates for patients with benign intracranial tumors when evaluated over the long term," said Douglas Kondziolka, M.D., principal investigator in the study and professor of neurological surgery and radiation oncology, vice chairman of education in the department of neurological surgery and co-director of the Center for Image-Guided Neurosurgery at the University of Pittsburgh Medical Center.
The study evaluated 285 consecutive patients who underwent radiosurgery for benign brain tumors between 1987 and 1992 at the University of Pittsburgh Medical Center. In the study, 157 patients had acoustic neuromas, 85 had meningiomas, 28 had pituitary adenomas, five had craniopharyngiomas and 10 had other cranial nerve schwannomas. Prior surgical resection had been performed in 44 percent of these patients and prior radiation therapy administered to 5 percent. Median follow-up of patients was 10 years. Mean patient age was 60 years.
The study found that tumor volume reductions usually occurred slowly, beginning as early as six months following the gamma knife procedure, but continuing even years later. The majority of tumors (63 percent) eventually reduced in size. Some tumors that had regressed by five years after radiosurgery were even smaller seven and 10 years later. Delayed tumor growth was identified in 5 percent of patients. Surgical resection after radiosurgery was performed in 13 patients (5 percent). No patient developed a radiation-induced tumor. After 10 years, 81 percent of patients were still alive. Normal facial function was maintained in 95 percent of patients who underwent gamma knife treatment for acoustic neuroma.
"Gamma knife radiosurgery appears curative for many patients with small or medium sized benign brain tumors," said Dr. Kondziolka. "Our study found that it was rare for a tumor to enlarge once four years of follow-up had passed. Similarly, radiation-related morbidity usually occurred early, within three years. We continue to recommend that imaging studies be obtained every four years, once 10 years of follow-up have been completed. Radiosurgery is best chosen for patients with tumors that do not cause significant symptoms from brain compression. For that reason, we recommend it for patients who have residual or recurrent tumors after resection, but also as an important choice for patients with newly diagnosed tumors."
Benign tumors of the brain and its coverings can lead to functional deficits that may persist for many years, which can lead to loss of independence, loss of employment, depression and the need for additional medical care.
The gamma knife contains 201 cobalt-60 sources of approximately 30 curies each, placed in a circular array in a heavily shielded unit. The unit directs gamma radiation to a target point. Such target points selected in the brain can be placed at the center of the radiation focus, allowing a radiation dosage to be delivered in one treatment session. Also involved in the study were; L. Dade Lunsford, M.D., professor and chairman of the department of neurological surgery and co-director of the Center for Image-Guided Neurosurgery at the University of Pittsburgh School of Medicine; John C. Flickinger, M.D., professor of radiation oncology and neurological surgery; Ajay Niranjan, M.B.B.S, M.S., M.Ch., research assistant professor of neurological surgery; Ann Maitz, M.Sc., assistant professor of neurological surgery and radiation oncology; and Narenda Nathoo, M.D. clinical fellow.
CONTACT:
Frank Raczkiewicz
Alan Aldinger
PHONE: 412-647-3555
FAX: 412-624-3184
E-MAIL:
RaczkiewiczFA@upmc.edu
AldiAL@upmc.edu