MGMT and central nervous system cancer: The major factors routinely assessed for gliomas studies include mutation in isocitrate dehydrogenase 1 (IDH1), the expression and mutation of the epidermal growth factor receptor (EGFR), the cell replication index reported as percentage of Ki67 expression, and the O6-methylguanine-DNA-methyltransferase (MGMT) promoter hypermethylation, the major predictive factor for treatment response to TMZ in GB patients (13, 14).