Carmustine wafers implanted into the post-surgical cavity provided a modest OS benefit in patients with newly diagnosed WHO grade 3 or 4 gliomas or recurrent glioblastoma61,62; however, in the pivotal trial of this approach, patient outcomes were not statistically significantly different after patients with WHO grade 3 tumours (the majority of which are now known to be IDH-mutant) were excluded from the survival analysis. Here, IDH2 is linked to glioma.