TO date, glioblastoma (GBM) remains an incurable disease that ipso facto urgently needs novel therapies. Maximal resection followed by radio-chemotherapy typically yields temporary disease control, and whereas this leads to prolongation of overall survival (OS), the outcomes are still dismal. 28, 29 More recently, tumortreating electrical field therapy was found to further increase the OS of these patients, reaching a new benchmark of 43% 2-year survival. 30 Whereas these therapies show some efficacy in the upfront setting, nearly all patients ultimately experience recurrence of disease. Unfortunately, to date there are no treatments that prolong survival for recurrent GBM. Several clinical trials testing immune checkpoint inhibitors (ICIs) in GBM are ongoing. However, it is expected that if a benefit is noted, it may be for a limited subset of patients. Therefore, strategies to optimize patient selection and timing of therapy might provide a means for effective immunotherapy for these tumors.