Patient characteristics and survival in patients with and without tumour samples sufficient for analysis of MGMT methylation and IDH1/2 respectively were compared; the only systematic difference was the extent of resection at initial surgery, the proportion of patients with biopsy alone being higher in the group for whom MGMT methylation and IDH1/2 analysis was not possible (e.g. 39% vs. 18% in patients where methylation analysis was possible). Here, MGMT is linked to neoplasm.