MGMT and glioblastoma: GBM is characterized by diverse genetic and epigenetic alterations, such as isocitrate dehydrogenase (IDH) 1/2 mutations, O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, epidermal growth factor receptor (EGFR) amplification, and EGFR variant III (EGFRvIII) expression [4,5,6,7].