MGMT and glioblastoma: In contrast, in both the VB-Glioma-III and the T-Glioma-II/III datasets basically all tumors clustering together displaying CIMP were classified as MGMT methylated by the MGMT-STP27 model (32/32 and 48/49), while the CIMP-negative tumors exhibited a methylation frequency of 54 % (19/35) and 50 % (11/22) that is similar to the three glioblastoma datasets (Figs. 5, 6).