Randomized trials of radiation therapy in adult low-grade gliomas.

There are two central questions in the radiotherapeutic management of the adult patient with a supratentorial low-grade (WHO grade II) astrocytoma, oligo-astrocytoma, or oligodendroglioma. The first question is one of timing. Following tissue diagnosis with or without maximum surgical resection, should immediate postoperative radiation therapy (RT) be given, or should RT be deferred to the time of local recurrence? The second question is one of dose. Assuming RT is given, should lower doses (ie, approximately 45-50 Gray (Gy)) or higher doses (ie, approximately 60-65 Gy) be administered? One Phase III prospective randomized clinical trial addressing the first question and two addressing the second question have been performed. Their results suggest that delayed (versus immediate) RT and low-dose (versus high-dose) RT are both acceptable treatment strategies despite the bias amongst radiation oncologists (primarily based on retrospective data) that immediate and high-dose RT would result in better outcome. The schema of the ongoing Radiation Therapy Oncology Group study is presented.