Gamma knife radiosurgery for malignant tumors.

Between May 1990, and June 1994, 79 patients with malignant tumors were treated radiosurgically using a Leksell gamma unit at Asan Medical Center. Of these patients, 57 were metastatic brain tumor, 12 were glioblastoma multiforme (GM), 4 were primitive neuroectodermal tumor, 3 were malignant germ cell tumor, 2 were recurrent lymphoma, and 1 was adenoid cystic carcinoma of the orbit. Among 57 patients with metastatic tumors, 28 patients harboring 60 tumors were followed clinically and radiographically. The median marginal dose for these tumors was 30 Gy and the median survival rate was 15 months. Twenty-one tumors disappeared and 32 tumors decreased in size during 2 to 6 months after radiosurgery on computed tomographic or magnetic resonance imaging scans. All 12 patients with GM were treated with conventional radiation (6,240 approximately 6,500 cGy) after surgical resection or biopsy prior to radiosurgery (13 approximately 15 Gy to margin). The results were varied. Radiosurgical treatment of two recurrent lymphomas and three recurrent mixed germ cell tumors after radiation and chemotherapy provided rapid clinical improvement with disappearance of the tumor. However, new lesions appeared in two lymphomas and one mixed germ cell tumor within 3 to 4 months. One patient with adenoid cystic carcinoma of the orbit, who was treated radiosurgically prior to resection, is alive without recurrence 31 months after the treatment. Gamma knife radiosurgery appears to be the best alternative method to surgical excision plus radiation therapy for single and multiple cerebral metastases. It also provides rapid palliation of symptoms due to recurrent malignant tumors. And it may have an adjuvant role in the treatment of some tumors delaying local recurrence, if given prior to resection. However, the preliminary results for the malignant gliomas were inconclusive.