IDH1 and central nervous system cancer: In grades III and IV gliomas with IDH mutations, the overall HR for OS was 0.19 (95% CI: 0.11–0.35, Pheterogeneity  = 0.579) and 0.39 (95% CI: 0.27–0.56, Pheterogeneity  = 0.065), respectively, compared with wild-type IDH (Table 3).