PATH-06. TRANSLATION INTO CLINICAL PRACTICE OF THE G1-G7 MOLECULAR SUBGROUP CLASSIFICATION OF GLIOBLASTOMA

Abstract Glioblastoma is the most frequent and malignant primary brain neoplasm. Glioblastoma growth is promoted by alterations in mediators from five major pathways: MAPK and PI3K canonical growth pathways, telomere elongation/TERT, cell cycle G1-phase and the p53 pathway. In a recent breakthrough study on a prospective Discovery cohort, I proposed the first all-inclusive molecular classification of glioblastoma into seven subgroups, G1-G7, based on MAPK pathway activation. New data from a subsequent, prospective Validation cohort validated the G1-G7 molecular subgroup classification, showing significant demographic and molecular differences between subgroups. Beside the initial histologic diagnosis, the G1-G7 classification requires next generation sequencing (NGS) of formalin-fixed paraffin-embeded (FFPE) samples and genomic-transcriptomic correlations between DNA mutations, copy number variations (CNVs) and RNA expression. Thus, in the Combined cohort containing tumors from over 220 glioblastoma patients, aproximately 75% of cases fell into three major subgroups, G1/EGFR, G3/NF1 and G7/Other, whereas the rest of 25% cases made up the four minor subgroups, G2/FGFR3, G4/RAF, G5/PDGFRA and G6/Multi-RTK. The name of the mutated most upstream, non-redundant, MAPK pathway effector corresponds to each subgroup, except for the G7/Other subgroup in which MAPK activation is minimal and PI3K pathway activation is dominant. The effectors of the other four pathways may be redundant; however, genomic-transcriptomic correlations showed subgroup specificity, with opposing trends for the G1/EGFR and G7/Other molecular subgroups. This first, all-inclusive, molecular subgroup classification of glioblastoma in a large prospective patient cohort allowed integrated pathway analysis, risk stratification and demographic comparison between Caucasian/White and African-American/Black patients. Most importantly, its implementation into clinical practice opened the avenue to controlled therapeutic approaches.