IDH1 and astrocytoma (excluding glioblastoma): In IDH-mutant astrocytomas, the TMB was significantly elevated between the initial presentation and recurrence in both those with acquired MMR gene mutations (P < .0001) and those without (P = .0353) (Figure 4); however, the mean difference between TMB in primary tumors and recurrence (ΔTMB) differed significantly between these two groups.