In this context, the lack of routine molecular data (e.g., IDH) during 2003–2017 may have inflated survival estimates for histology-defined “glioblastoma” by pooling cases that, under WHO 2021, would be classified as astrocytoma, IDH-mutant, grade 4, which typically show longer survival than glioblastoma, IDH-wildtype. Here, IDH1 is linked to glioblastoma.