Identifying factors to predict benefit from bevacizumab in progressive glioblastoma multiforme (GBM).

e13515Background: Bevacizumab (BEV) has demonstrated activity in GBM, but the benefits have not been clearly defined in prospective randomised phase III trials. Some patients continue BEV for extended periods but little is known about predictors of clinical benefit. It has been suggested that a less intensive dose schedule might offer similar benefits. Methods: In a retrospective analysis of a National Neuro-Oncology centre database we examined biomarkers of BEV benefit on overall survival (OS), including age at diagnosis, time from diagnosis to BEV start, MGMT methylation and IDH-1 status. We compared those who derived clinical benefit (OS of ≥6-months) to those with limited clinical benefit (OS <6 months). At our Institution, there is variable practice between Neuro-Oncologists in terms of BEV dose schedule. In this homogeneous patient population, we examined whether OS was similar for patients who received standard BEV dosing (10mg/kg q 2wks or 15mg/kg q 3wks) or reduced intensity BEV (5mg/kg q 2wks or...