RADT-26. RADIATION FRACTIONATION IN THE MANAGEMENT OF ELDERLY PATIENTS WITH GLIOBLASTOMA BY AGE

Abstract Multiple studies have investigated hypofractionated radiation (HFX) for elderly patients with glioblastoma (GBM), using varying age cut-offs. This leads to uncertainty about who benefits most from a hypofractionated course. This study examines the use of and outcomes with HFX, between two commonly used cut offs to define elderly GBM: 65 versus 70 years old. In this retrospective review, 309 patients diagnosed with GBM who were treated with radiation at a single academic institution were included. The Kaplan-Meier method was used to analyze overall survival. A Chi-square test was conducted to compare the use of SFX and HFX and the median survival between those 65-69 versus 70-74 years old. Patients aged 70-74 were more likely to receive HFX radiation compared to those aged 65-69 (80.00% vs. 42.65%, p=0.0002). Median survival for the entire cohort was 12 months. Among those 65-69 years old, SFX was associated with a significantly higher median survival compared to HFX (14 months vs. 7 months, HR 2.00, 95% CI 1.16 – 3.46, p=0.03). This was also true for those 70-74 years old, (18 months vs. 4 months, HR 4.50, 95% CI 1.84 – 11.01, p=0.03). We demonstrate a decrease in the use of SFX in patients 65 years or older, and that that standard fractionation is associated with longer survival in older patients with GBM. This suggests that in a well selected population, SFX should be considered even among elderly patients. Additional work is needed to determine whether these findings are causal or due to patient selection. Performance status and MGMT methylations status, for instance, should guide clinical decision making. Such results highlight the importance of further studies to fine tune radiation dose and fractionation elderly patients with GBM.