Brain Metastases of a Triple-Negative Breast Cancer: A Systematic Literature Review of the Systemic Treatment Options

Based on the current evidence discussed in this review, testing for programmed death-ligand 1 (PD-L1), HER2, including immunohistochemistry (IHC) status as well as germline BRCA 1/2 mutation, should be considered in all mTNBC patients with BM as the results have significant treatment implications. Moreover, PD-L1 expression should be evaluated on primary tumor and (if tissue sample available) reevaluated on BMs if negative on primary BC, to maximize the opportunity for treatment with immune checkpoint inhibitors. Furthermore, if brain tissue is available, HER2 IHC should also be tested in order to evaluate the status switch and to assess the therapeutic effectiveness of treatment with T-DXd. Further targeted agents are urgently needed in order to improve the survival of patients with TNBC and BM.