Pembrolizumab efficacy in a tumor mutation burden-high glioblastoma patient: A case study and implications for precision oncology.

A glioblastoma (GBM) patient with a high tumor mutation burden (TMB-high) and mismatch repair deficiency (dMMR) exhibited a significant response to pembrolizumab, an immune checkpoint inhibitor (ICI), despite prior treatment with temozolomide (TMZ), known to induce hypermutation and potential resistance to ICIs. The rapid disease progression, indicated by 80% Ki67 positivity, was markedly countered by the positive outcome of pembrolizumab treatment. This case challenges traditional GBM treatment paradigms, demonstrating the potential of precision oncology in patients with significant TMB and dMMR, and underscores the importance of comprehensive genomic profiling in guiding clinical decisions in GBM management.