IDH1 and astrocytoma (excluding glioblastoma): More complete resection with lower residual T2-weighted tumor volumes was also associated with favorable survival in 113 patients with IDHmt astrocytomas, of which 86 patients had grade 3 histology (and the remaining 27 patients had grade 4 histology); this finding was confirmed in other retrospective studies on astrocytomas grade 3 and 4.37,38,41 A small single-institutional study on patients with grade 3 IDH-mutant and 1p/19q-codeleted oligodendroglioma failed to detect an association between the extent of resection and survival.42