Modern aspects of radiation therapy for glial tumours of the brain.

Radiation was conclusively proved to be of value in the treatment of malignant gliomas in the late 1970's where it enabled an approximate doubling of the survival time. Further study defined a number of prognostic factors which provide a basis for selecting patients for treatment. The introduction of computer tomography (and later magnetic resonance) scanning allowed a more rational approach to target volume definition and a reduction in radiation-related morbidity. Dose-ranging studies defined a standard approach to treatment (60 Gray in 30 fractions). Since then numerous attempts have been made to improve on these results. Marginal benefits have been claimed for altered fractionation schemes, limited volume dose escalation (implants and stereotaxy), radiation sensitisers and particle therapies. However none has become routine in clinical practice. Advances in planning technology have allowed a further reduction in the volume of normal brain irradiated and the potential for dose escalation. Low grade astrocytoma has not been examined in the same way and great doubt exists with respect to optimal treatment. There is a great opportunity for research to realise the potential in the new techniques for improving the outlook for patients with malignant glioma and in clarifying the role of radiation in low grade tumours.