At interview, participants were aged on average 50.4 years (range 22–69 years); male (n = 16), female (n = 12); diagnosed with a grade 2 oligodendroglioma (n = 10: IDH1‐mutant, yes n = 7, no n = 2, unknown n = 1; 1p/19q codeletion, yes n = 9, unknown n = 1), grade 3 oligodendroglioma (n = 9: IDH1 mutant, yes n = 6, no n = 1, unknown n = 2; 1p/19q codeletion, yes n = 7, unknown n = 2), or grade 2 astrocytoma (n = 9: IDH1‐mutant, yes n = 6, no n = 1, unknown n = 2; 1p/19q codeletion, no n = 7, unknown n = 2) (Table 3). This evidence concerns the gene IDH1 and oligodendroglioma.