NIMG-51. RADIOLOGIC PHENOTYPES ARE TREATMENT SPECIFIC AND ASSOCIATED WITH SURVIVAL - EXPLORATORY ANALYSIS OF EORTC 26101

Abstract

BACKGROUND: EORTC 26101, a randomized phase III trial in recurrent glioblastoma compared lomustine plus bevacizumab to single agent lomustine. In this exploratory analysis the tumors were radiologically followed and characterized with the objective to investigate whether type of radiologic progression differs between the treatment groups and is related to outcome. METHODS: Five progression types (PTs) were categorized using an adapted algorithm according to MRI contrast enhancement behavior in T1 and T2‐weighted images in 373 patients (lomustine, n=129; combination, n=244). Frequencies of PTs (designated as cT1 relapse, classic T1, T2 diffuse, T2 circumscribed and primary non‐responder), time to progression (PFS) and overall survival (OS) were assessed. Frequencies were compared by Wilcoxon rank test, univariate associations of PTs with survival were tested by log‐rank test, hazard ratios (HR) with 95% Confidence interval were calculated by Cox model. RESULTS: Except for “classic T1”, frequencies of PTs differed between the treatment arms, with non‐enhancing tumor progression (T2 diffuse and T2 circumscribed) being more commonly detected in the combination group. Complete resolution of contrast enhancement (cT1 relapse) during treatment was associated with better survival than mere decrease (classic T1) of contrast enhancement (PFS; HR=0.57 [0.29.;1.11]) and OS; HR=0.42 [0.15;1.18] for lomustine, PFS; HR=0.33 [0.23;0.45] and OS; HR=0.37 [0.26;0.52] for combination group. CONCLUSIONS: Progression of glioblastoma can be characterized radiologically. These radiologic phenotypes are influenced by treatment and are associated with differential outcomes. Complete decrease of contrast enhancement during treatment is associated with longer PFS and OS.