HOUT-19 OBJECTIVE There are limited evidence-based guidelines for treatment of elderly glioblastoma (GBM) patients. This analysis explores prognostic indicators that may help guide treatment in this population. METHODS This retrospective analysis includes 106 patients 75 years old seen at the Preston Robert Tisch Brain Tumor Center between 2004–2016. Kaplan-Meier methods estimated overall survival (OS). Time to OS was censored at last follow-up for patients still alive. Univariate Cox proportional hazards models assessed predictors of OS. RESULTS Median age at diagnosis was 79 years (range: 75–93). Median follow-up was 68.8 months. Median survival was 8.1 months (95% CI: 6.5, 9.3). Patients with biopsy-only had significantly worse OS than patients with gross total resection (GTR) (Hazard Ratio (HR)=2.64 (95% CI: 1.69, 4.12); p<0.001) or subtotal resection (STR) (HR=2.54 (95% CI: 1.33, 4.85); p=0.005; OS=5.0 vs 9.8 vs 12.7 months, respectively). Of 84 patients with data available regarding radiotherapy (RT), there was no significant difference in OS between patients receiving 3 weeks of RT versus 6 weeks. Patients not receiving RT had significantly worse OS than patients with 3-week (HR=7.66 (95% CI: 3.25, 18.03); p<0.001) or 6-week courses (HR=8.95 (95% CI: 4.16, 19.27); p<0.001; OS=4.5 vs 9.2 vs 11.2 months, respectively). Patients with biopsy-only tended to have lower KPS and were less likely to receive RT. In the subset of 66 patients with known methylation status, unmethylated patients showed a trend towards worse OS than methylated patients (OS=7.5 vs 11.5 months, respectively; HR=1.65 (95% CI: 0.987, 2.759); p=0.056). A post-op KPS80 was predictive of better OS (9.3 vs 5.4 months; HR=0.976 (95% CI: 0.954, 0.999); p=0.043). CONCLUSIONS Biopsy-only, no RT, lower KPS and absence of MGMT methylation were associated with worse OS. Extent of resection (STR vs GTR) and duration of radiation (3 weeks vs 6 weeks) did not influence OS.