MGMT and astrocytoma (excluding glioblastoma): Significantly, in adults, molecular alterations in this class of metabolic gene are now recognized as a defining molecular event commonly frequent in the secondary GBMs (50%), which are also known by O6-methylguanine-DNA methyltransferase promoter methylation (MGMT) (75%) (20), as well as in the majority of lower-grade astrocytoma (WHO grade II and III gliomas) (80%), which are also both reported by tumor protein (TP53) mutations and functional loss (mutation or deletion) of α-Thalassemia/Mental Retardation Syndrome X-linked (ATRX) (24, 25).