IDH2 and central nervous system cancer: IDH mutations were a significant prognostic marker for PFS in grade III (HR  = 0.17, 95% CI: 0.05–0.58, Pheterogeneity  = 0.000) and grade IV gliomas (HR  = 0.67, 95% CI: 0.40–1.13, Pheterogeneity  = 0.000; Table 3).