IDH1 and astrocytoma (excluding glioblastoma): As in large registries17, the majority of tumors were histologically classified as astrocytomas, making up roughly 2/3 of cases in both the training and validation cohort, and patients with an IDH wild type tumor tended to be older (mean age 47 years) than patients with an IDH mutant tumor (mean age 39 years, Welch t test, p = 0.1).