The Neuro-Oncology Disease Site Group (DSG) reviewed the evidence and developed recommendations to address the following clinical questions: 1) What is the role of radiotherapy in adult patients with newly diagnosed malignant glioma? 2) If radiotherapy is offered, what are the optimal radiotherapy characteristics? This practice guideline report has been reviewed and discussed by the Neuro-Oncology DSG on several occasions and it was approved with the addition of the following general comments.
Many of the studies discussed in this systematic review were performed over the last two to three decades. There have been major technological advances in both the delivery of radiotherapy and in diagnostic imaging in the last five to ten years, such that results and recommendations based on these older data may no longer be pertinent. Until new evidence emerges revisiting many of the issues raised in this guideline, the DSG agreed that the current recommendations apply. However, the most recent literature search update provided sufficient evidence to recommend the addition of concurrent temozolomide (TMZ) to conventional radiotherapy regimens.
Additionally, most of these older studies did not address toxicity or quality of life. This is particularly pertinent for studies where higher intensities of therapy were being investigated. It is very possible that higher intensity therapies may prolong life but at a significant cost in terms of quality of life, such that patients and physicians should have this information available to be able to make informed choices among the therapeutic options. It is strongly recommended that future studies in patients with brain tumours include measures of toxicity and quality of life.
Postoperative radiotherapy as an appropriate recommendation for patients is well supported by randomized studies and remains standard therapy. With regard to the dose issue, only the Medical Research Council (UK) study of 60 Gy in 30 fractions compared with 45 Gy in 20 fractions showed a small statistically significant benefit for the higher dose. No other randomized studies of dose escalation have shown any benefit compared with conventional doses in the range of 50 to 60 Gy. For this reason, the DSG felt that doses of 60 Gy with conventional fraction sizes were acceptable, particularly in view of the fact that higher doses are likely associated with higher toxicity and increased costs and inconvenience for the patient, in a disease which remains incurable.
The hypofractionated dose utilized in the study by Glinski, given over three months, is an extremely unusual fractionation, and one that the DSG does not recommend.
All other studies of hyperfractionation, radiation sensitizers, or particle therapy have thus far failed to demonstrate a benefit, and these approaches remain within the domain of experimental therapy. In view of the poor results of conventional radiotherapy in this disease, the DSG recommends that patients be encouraged to participate in properly conducted experimental studies.