Long-term outcome of low-grade oligodendroglioma and mixed glioma

Background: Low-grade oligodendrogliomas and mixed gliomas can be indolent and remain unchanged for years. Optimal timing and effectiveness of initial treatment is uncertain and therapy can be associated with toxicity. Methods: Retrospective review of patients diagnosed between 1979 and 1997 with low-grade oligodendroglioma or mixed glioma. Time to progression, survival, prognostic factors, and treatment toxicities were evaluated. Results: A total of 106 patients (77 oligodendroglioma, 29 mixed glioma) were identified; median age was 36.7 years. Initial presenting symptoms were seizures in 76 (72%) and headache in 11 (10%); tumor was diagnosed as an incidental finding in five patients. Tumor progression was diagnosed in 72 patients (68%). Overall median time to progression (MTTP) was 5.0 years (range 0.5 to 14.2). Median overall survival (OS) was 16.7 years. No prognostic factors reached statistical significance. MTTP and OS were not significantly affected by treatment. Of 62 patients who received radiation therapy, 9 (15%) developed radiation necrosis and 13 developed radiation therapy-related cognitive changes, requiring ventriculoperitoneal shunting in six. Significant myelosuppression was seen in 35 of 76 (46%) patients treated with chemotherapy. Conclusions: Low-grade oligodendroglioma and mixed glioma have a long median overall survival. There were no apparent differences;in either immediate versus deferred treatment or choice of initial therapy on disease-free or overall survival. Chemotherapy was associated with significant acute toxicity in almost one half of patients; radiation therapy produced late neurotoxicity in one third, justifying deferred treatment until clinically necessary.