Acquired PTEN Loss May Mediate Dabrafenib and Trametinib Resistance in BRAF V600E-Mutated Epithelioid Glioblastoma: A Case Report and Literature Review

Abstract

Epithelioid glioblastoma is a rare and aggressive variant of glioblastoma that is common in children and young adults. This variant frequently has a BRAF V600E mutation, and in recent years, this is often treated with BRAF and mitogen-activated protein kinase kinase inhibitors. An 18-year-old female initially presented with headaches and vomiting. They were diagnosed with an epithelioid glioblastoma and treated with temozolomide chemoradiotherapy. Upon progression, they had to redo surgery and then received dabrafenib and trametinib. They had one last surgery shortly before fatal tumour progression. Retrospective molecular analysis of three tumour specimens showed a PTEN mutation that arose upon first progression, but was not there initially. There were no new tumour mutations after initiation of dabrafenib and trametinib. The acquired PTEN mutation may have conferred resistance to dabrafenib and trametinib. This case highlights the potential importance of early treatment with BRAF and mitogen-activated protein kinase kinase inhibitors in high-grade BRAF V600E-mutated gliomas, ideally before the tumour develops resistance to targeted therapy.