MGMT and glioblastoma: Detection of methylation within the promoter region of O6-methylguanine-DNA methyltransferase (MGMT) gene has clearly provided the most meaningful clinical correlation and is generally accepted as a predictive and prognostic biomarker in temozolomide treated GBM, even in elderly patients (Stupp et al., 2005a, 2009; Reifenberger et al., 2012; Wick et al., 2012).