RT-35 * ELAPSED DAYS AFTER RADIOTHERAPY FOR GLIOBLASTOMA

Abstract

BACKGROUND: There have been conflicting reports regarding the effect of delayed radiation therapy after surgical resection of glioblastoma (GBM) on outcomes. We sought to investigate whether the timing of adjuvant radiotherapy (RT) impacted survival of patients at our institution. METHODS: We reviewed all patients treated with radiotherapy for GBM at our institution. Variables included in our analysis were age, Karnofsky Performance Status (KPS), type of surgery, length of hospital stay, receipt of temozolomide (TMZ), RT duration, RT technique, total RT dose, interval between surgery and RT, and tumor molecular status including isocitrate dehydrogenase 1 (IDH-1) and O-6-methylguanine-DNA methyltransferase (MGMT). Survival was calculated using the Kaplan-Meier Method. RESULTS: From 1998 to 2013, 419 GBM patients were treated with radiotherapy of which 239 were men (57.0%). The median age was 60 years (range 18–91). The median survival for the entire cohort was 339 days (11.1 months). 151 patients started radiotherapy after surgery 5 weeks (20.8%). On univariate analysis age, KPS, type of surgery, length of hospital stay, RT duration, RT technique, total dose and interval between surgery and RT were significant predictors of mortality. IDH-1 (p = 0.17) and MGMT (p = 0.18) mutated status showed a trend towards better survival. Patients who started RT 5 weeks after surgery with the 1-year actuarial overall survival: 52.4%, 63.6% and 63.9%, respectively. On multivariate analysis only age, KPS, type of surgery, and total RT dose were significant predictors of survival; while interval between surgery and RT was not. CONCLUSIONS: We observed no detriment to delaying RT after surgical resection of GBM, and in fact, a small benefit to deferring RT until 3 weeks after surgery was observed on univariate analysis.