The DNA methylation status can indicate acquired resistance to a certain treatment, and therefore tracking those alterations could guide the modification of treatment.95 When Wang et al.96 analysed the serum and CSF of patients with different grades of glioma, they detected the presence of methylation in the MGMT promoter, by using methylation-specific PCR, in 38 patients with GBM out of 89 glioma patients (42.6%). Here, MGMT is linked to glioblastoma.