IDH1 and central nervous system cancer: Other variables, age (HR = 2.614, 95% CI 1.881–3.631) and tumor grade (HR = 8.772, 95% CI 5.97–12.888) were also risk factors for poor prognosis in high-grade gliomas; conversely, some variables such as IDH-status, chr-1p-19q-codeletion, MGMT-promoter-status and chemotherapy delayed the development of high-grade gliomas and had a better prognosis and increased survival time.