We have shown that overall CNA level at the time of initial surgery is an independent prognostic factor in IDH-mutant astrocytoma, in which cases with CNA comprising ≥ 15% of the total genome (approximately 465 Mbp) have significantly worse Karnofsky performance status, progression-free survival, and overall survival compared to their counterparts with relatively low CNA [125, 150, 151, 174–176], a finding which was validated in other glioma cohorts and other cancers, although the particular CNA threshold varied somewhat [10, 190, 212]. The gene discussed is IDH2; the disease is astrocytoma (excluding glioblastoma).