The data include: the number of glioblastoma samples analyzed by pyrosequencing and the fixation method, study type (whether prospective or retrospective and whether a clinical trial with homogeneous therapy or not), analyzed region (as the consecutive CpG numbers within the MGMT CpG island), applied threshold (all values listed if samples were divided into more than 2 groups; if different threshold values were used for the various sites, the range is shown in parentheses). The gene discussed is MGMT; the disease is glioblastoma.