This G-CIMP-low subgroup has a lower level of methylation at some CpG sites and comprises a minority of IDH-mutant astrocytoma cases with significantly worse overall survival, relative to G-CIMP-high astrocytomas, although there is a general trend toward conversion from G-CIMP-high to -low with recurrence and progression in grade [38, 55, 121, 134]. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).