Corticosteroid treatment modulates immune cell populations in the glioblastoma microenvironment

Abstract Background Corticosteroids play a crucial role in alleviating tumor-associated edema in patients with brain tumors. However, their impact on the tumor microenvironment within glioblastoma remains largely unexplored. In the context of increasing interest in immunotherapy and limited clinical progress for glioblastoma patients, it is important to understand how corticosteroid therapy influences the immune microenvironment. Methods This study involved 80 glioblastoma patients, 41 of whom received corticosteroids preoperatively and 39 who did not. The groups were balanced for key clinical prognostic parameters. Through immunohistochemical staining and image analysis-based software classifiers, we quantitatively assessed a broad marker panel covering immune, myeloid, hypoxia-related, and tumor-associated features of the glioblastoma microenvironment. Results Our analysis revealed a more than two-fold decrease in FOXP3+ regulatory T cells in glioblastoma tissue samples from patients who received corticosteroids. In dose-subgroup analyses, high-dose corticosteroid exposure was associated with increased CD68+ and CD204+ myeloid/macrophage-marker abundance. CD8 and CD4 T cell counts, as well as CD86, TMEM119, HIF-1α, PD-L1, and SOX2, remained similar across all groups. Conclusions Our findings suggest that corticosteroid treatment is associated with selective changes in T cell and myeloid/macrophage-marker abundance within the tumor microenvironment. These findings highlight corticosteroid exposure as an important factor to consider when interpreting immune profiles and developing immune-based therapies in glioblastoma.