Evaluation of gamma knife radiosurgery in the treatment of oligodendrogliomas and mixed oligodendroastrocytomas

Object. Radiosurgery is commonly used for the treatment of patients with glioma. The goal of this study was to evaluate the safety and efficacy of radiosurgery in the management of patients with oligodendrogliomas (ODGs) or mixed oligoastrocytomas (OGAs). Methods. A retrospective chart review of patients treated between May 1990 and January 2000 identified 18 patients (21 tumors) with either an ODG (10) or a mixed OGA (11) who had undergone radiosurgery. The median patient age was 43 years (range 23-67 years). Sixteen patients had undergone one or more tumor resections before radiosurgery; in two patients biopsy sampling alone had been performed. Tumor grades at the most recent operation were Grade 1 (one), Grade 2 (one), Grade 3 (12), and Grade 4 (seven patients). Seventeen patients had undergone prior radiotherapy; 11 were treated with chemotherapy before radiosurgery, and one had undergone a prior linear accelerator-based radiosurgery treatment. The median tumor volume was 8.2 cm³ (range 1.9-47.7 cm³); the median margin dose was 15 Gy (range 12-20 Gy); and the median maximum dose was 32 Gy (range 24-50 Gy). In this heterogeneous group, 12 patients died whereas six remain alive. Survival after radiosurgery was 78%, 61%, and 44% at 12, 24, and 48 months, respectively. Factors associated with an improved survival rate included younger age and smaller tumors. Conclusions. For patients with oligoastroglial tumors that have failed to respond to conventional therapies, radiosurgery may provide some survival benefit. Further study is needed to determine which subpopulation of these patients will have the best chances of enhanced survival from this treatment.