For GBM identified prognostic factors include patient age, performance status (PS), extent of resection (EoR), corticosteroid use at start of treatment and methylation of the gene promoter of O6-methylguanine-DNA-methyltransferase (MGMT) (40, 41), a DNA repair protein inhibiting the effect of TMZ (42). Here, MGMT is linked to glioblastoma.