P14.59 Rapid early progression of glioblastoma is not related to cortical/neural stem cells regions

Abstract BACKGROUND Rapid early progression (REP) of glioblastoma after surgery observed on pre-radiotherapy MRI scan is common. Subventricular zone (SVZ) and hippocampal regions are supposed to harbor astrocyte-like neural stem cells (NSC) with tumors arising from these transformed stem cells threatening of higher risk of REP. REP is defined as a new enhancing tumor or >25% increase in enhancement before radiotherapy. Lim′s classification of initial glioblastoma location related to these NSC regions predicts invasive and multifocal tumor phenotype. Glioblastomas are classified preoperatively into four groups by the spatial relationship of the contrast-enhancing lesion with the SVZ and cortex. The aim of this retrospective single-institutional study is to evaluate the relations of this Lim classification on REP in unselected cohort of glioblastoma patients. MATERIAL AND METHODS Patients receiving radiotherapy between 2014–2017 were analyzed, 95 were evaluable. 47 patients (30.5%) were treated with the Stupp regimen. Lim1 classification (contact with cortex as well as SVZ) was presented in 74(48%) patients, Lim2 (contact with SVZ only) in 22(14.3%), Lim3 (contact with cortex only) in 50(32.5%) and Lim4 in 8(5.2%) patients. A total of 52% of patients developed REP. RESULTS Significantly better overall survival was with Stupp regimen (23.3 vs. 8.6 months, p