Supratentorial malignant glioma: an analysis of radiation therapy in 178 cases

Abstract

To analyze treatment results of supratentorial malignant gliomas in the megavoltage era, all the histologic specimens were reviewed and glioblastoma multiforme (GBM) was distinguished from anaplastic astrocytoma (AA) by the presence of necrosis. Among those who had completed radiotherapy and who had been followed for at least one year, 135 GBM and 43 AA patients were found. The median survival time (MST) after operation was 12 months for GBM and 18 months for AA. The 5-year survival rate was 0.9% for GBM and 18% for AA. The size of radiation field had little influence on survival time; MST was 12 months for GBM patients treated with a local field covering tumor plus less than 2 cm margin, 12 months for those treated with a generous field (2 cm or more margin), and 13 months for those treated to whole brain. Also for AA, whole brain radiation did not prolong survival. Initial relapse of GBM and AA developed within the irradiated volume in 86% of the cases treated with a generous field. Whole brain radiation seemed useless for the treatment of malignant gliomas. Survival time appeared to be dose-dependent; MST was 10, 13, and 16 months for GBM patients who received 45–57, 57–63, and 63–72 Gy, respectively. Extensive surgical resection was associated with a better prognosis in GBM. AA patients 60 years old or older had a poorer prognosis than younger patients, but age was not a significant prognostic factor for GBM. Chemotherapy appeared to prolong survival slightly without improving long-term survival. Currently, an accelerated hyperfractionation regimen is being tested in which 1.5 Gy is given twice a day up to 69 Gy. Preliminarily, this regimen had no acute or late toxicity and yielded a survival rate at least equivalent to the conventional regimen.