As for glioblastoma, chemotherapy was frequently not sustained for ≥6 cycles, which were achieved, for example, by only 72% and 56% of elderly patients in France receiving TMZ and PCV, respectively, for high-grade IDH-mutant gliomas, while 19% and 87% in needed to reduce their chemotherapy dose (143). This evidence concerns the gene IDH1 and glioblastoma.