Low tumor mutational burden and immunotherapy in gliomas

In a recent article, Merchant et al. [ 1. Merchant M. et al. Tumor mutational burden and immunotherapy in gliomas. Trends Cancer. 2021; 7: 1054-1058 Google Scholar ] concluded that tumor mutational burden (TMB) is not useful in identifying patients with glioma who are responsive to immunotherapy. Indeed, the literature to date largely indicates that, in contrast to other tumor types, high TMB is not predictive of longer survival after immunotherapy in gliomas. Moreover, we agree with the perspective that this outcome is likely due to the distinct biology of gliomas and that alternative mechanisms of immune evasion and mutational characteristics that may explain this discrepancy should be explored. However, we point out that multiple recent studies have indicated that low TMB may be predictive of immunotherapy response in recurrent grade IV glioma (rGBM).