Normal Tissue Tolerance for High-Grade Gliomas: Is It an Issue?

In this article, we address the currently accepted dose tolerance parameters for the treatment of high-grade gliomas. The issue of normal tissue tolerance is becoming increasingly important because of the long-term survival of a significant subset of young, good performance status patients and the use of hypofractionated regimens for elderly patients with poor performance status. In addition, we address relevant clinical endpoints including clinical, pathologic, and radiographic changes and highlight the difficulty in discriminating between tumor-related and treatment-related effects. Finally, we review relevant clinical trials addressing issues of dose and/or volume parameters. Future trials for patients with high-grade gliomas should consider the inclusion of a prospective evaluation of neurocognitive function and imaging correlates of the brain to assist in the prediction, prevention, and treatment of radiation-induced damage of normal brain tissue.