Aberrations of molecular markers such as O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation, codeletion of 1p and 19q, isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) mutation, telomerase reverse transcriptase (TERT) promoter mutation, TP53 mutation, and epidermal growth factor receptor (EGFR) overexpression show prognostic significance to guide treatment decisions of GBM patients. The gene discussed is IDH1; the disease is glioblastoma.