The study population included 104 adult patients with a histologically confirmed supratentorial WHO grade 2 astrocytoma (IDH1/2 mutant, ATRX mutant, n = 70) or oligodendroglioma (IDH1/2 mutant, 1p19q codeleted, n = 34). This evidence concerns the gene ATRX and astrocytoma (excluding glioblastoma).