While some centres have started to manage IDH-mutant CDKN2A/B HD astrocytomas using the EORTC-NCIC protocol for IDH-wildtype glioblastomas, historically most of these cases would have been treated as lower-grade (Grade 2 and 3) gliomas with radiation therapy and sequential chemotherapy. This evidence concerns the gene CDKN2A and astrocytoma (excluding glioblastoma).