MGMT and glioblastoma: Traditional prognostic markers of GBM, such as O(6)-methylguanine-DNA methyltransferase (MGMT) methylation, IDH mutation, epidermal growth factor receptor (EGFR) variant III (EGFRvIII), phosphatase and tensin homolog (PTEN) deletion, and vascular endothelial growth factor (VEGF) expression, improved our understanding of the disease; however, the fact of the matter is that the overall survival of patients has not significantly changed over the years [86].