MGMT and glioblastoma: In multivariate survival analysis, including known prognostic GBM markers (i.e., expression of O-6-Methylguanine-DNA Methyltransferase (MGMT) in the primary tumor and age at diagnosis), there was no association between responder type and progression-free (P = 0.59, β=  − 0.86) or overall (P = 0.97, β = 0.1) survival.