Subset analyses of the RTOG 9402 and EORTC 26951 do not demonstrate a survival benefit for adjuvant PCV for non‐1p/19q codeleted gliomas, however secondary analyses of RTOG 9802 and RTOG 9402 demonstrated survival benefit in any IDH mutant lower grade gliomas, regardless of 1p/19q codeletion status. This evidence concerns the gene IDH1 and glioma.