Purpose: To retrospectively analyze the outcomes and benefits from radiation therapy (RT) as a component of multimodal treatment for oligodendroglioma and oligoastrocytoma, assessing local control and survival rates and evaluating prognostic factors.
Methods and materials: We retrospectively reviewed 56 adult patients with supratentorial oligodendroglioma or oligoastrocytoma treated at our institution from January 1990 to December 2003 with fractionated stereotactic RT (FSRT).
Results: Fractionated stereotactic RT was well tolerated in all patients, without side effects. Median survival and progression-free survival calculated from the initiation of radiotherapy were 48 months (range, 2-133 months) and 38 months (range, 2-132 months), respectively. Progression-free survival rates after radiation were 89% at 1 year and 52% at 5 years. Of 26 recurrences, 92% developed in field. With regard to histology, overall survival rates in the World Health Organization (WHO) Grade II group were 89% and 74% at 5 and 10 years, respectively. In patients with WHO Grade III tumors, overall survival rates at 5 and 10 years were 69% and 46%, respectively. No prognosticators could be identified for median survival and progression-free survival after radiotherapy. Median overall survival calculated from primary diagnosis was 77.5 months (range, 3-214 months). The Cox regression multivariate analysis for age and neurologic symptoms showed a significance of p = 0.003 for age and p = 0.037 for the presence of neurologic symptoms on overall survival since primary diagnosis.
Conclusions: Commonly, conventional conformal RT is applied in the treatment of brain tumors. In FSRT, the tumor volume can be irradiated with high doses, sparing volume of normal brain tissue. Our data are in accordance with survival times found in the literature. Ninety-two percent of all recurrences occurred within the defined target volume, confirming that reduction of the RT portals by the use of FSRT does not lead to an increased rate of recurrences at the field border or out of field. Fractionated stereotactic RT can therefore be implemented as an effective and safe modality in the therapy of primary oligodendroglioma and oligoastrocytoma.