We also observed sex differences in the percentage of GBM patients with MGMT methylation, similar to a 2008 study of 371 primary GBM patients where Zawlik et al. first reported that females more often have MGMT promoter methylation compared to males (53% vs. 39%; p = 0.0106), similar to our findings [4]. This evidence concerns the gene MGMT and glioblastoma.