Supratentorial Low-Grade Astrocytomas in Adults

Abstract

Summary: Approximately one-third of newly diagnosed primary glial tumors in adults are low-grade astrocytomas. With the development of more sensitive radiological techniques, these tumors are being detected earlier in their history, and thus the patients often have minimal or no neurological impairment. Lowgrade astrocytomas are thought to have a good prognosis. However, their clinical behavior is variable and they often dedifferentiate to a more aggressive, high-grade glioma. Because of the lack of prospective, randomized studies, the role of surgery and radiation in the management of these lesions is controversial. We review the pathology, history, and clinical and radiological characteristics of low-grade astrocytomas and the clinical studies that examine the role of surgery and radiation therapy. Based on this review, the following recommendations are made: (1) treatment should be based on the histological type (astrocytoma, pilocytic astrocytoma, and gemistocytic astrocytoma); (2) magnetic resonance imaging is the modality of choice for diagnosis and surgical planning; (3) radical total resection should be attempted whenever safely possible; (4) multiple biopsies should be examined pathologically to avoid sampling errors; (5) patients with the astrocytoma histologic type who have a total resection can be followed clinically and with frequent magnetic resonance imaging scans, whereas those who have a subtotal resection should receive adjuvant radiation therapy in a conventional fractionated schedule with a dose of 4,500 to 5,500 rad to a limited volume of brain; (6) complete resections of pilocytic astrocytomas may be curative; (7) the benefit of radiation in patients with subtotally resected pilocytic astrocytomas is not well defined; (8) patients with gemistocytic astrocytomas should receive adjuvant radiation therapy regardless of the extent of resection, because of the high incidence of dedifferentiation to a high-grade glioma in these patients; and (9) lesions discovered as incidental findings can be managed conservatively by serial radiological observations.