Radiation Therapy of Malignant Gliomas

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Abstract
Besides local resection, external radiation therapy (EXRT) plays the major role in the treatment of malignant glioma. With postoperative EXRT, median survival is increased to 9-12 months for glioblastoma multiforme (GBM), as compared to 4-5 months after surgery alone (median survival for anaplastic astrocytoma (AA): 27 months – 3 years). The target volume should include 2 cm beyond that indicated by CT and MRI. For treatment planning computed tomography in treatment position is mandatory, and an individualized face mask for immobilization of the head should be used during the whole process of treatment planning and treatment delivery. With conventional fractionation, a total dose of 60 Gy seems to be adequate. There is no evidence that the application of higher total doses, of hyperfractionated XRT, of radiosensitizers or of fast neutron radiotherapy can improve treatment results. The role of high precision single-dose stereotactic irradiation and of brachytherapy is undefined. For both techniques, it seems difficult to control AA or GBM at the perimeter of the tumor which is a frequent site of failure. The use of the chlorethyl nitrosoureas (e.g. BCNU, ACNU) is the most effective and frequent form of chemotherapy for malignant glioma. Adding chemotherapy to postoperative radiotherapy leads to an increased percentage of 18-month survivors, but the improvement of median survival for the whole group of patients is within several weeks. Prognostic factors such as grade, performance status, and age may considerably influence treatment results and treatment strategies. In severely compromised patients, treatment time may be reduced by altered fractionation schemes, and chemotherapy seems to be debatable.

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