Breast Cancer Brain Metastasis: Bridging Biological Mechanisms to Therapeutic Innovations

Abstract

Breast cancer brain metastasis (BCBrM) remains a major clinical challenge with limited therapeutic options and poor prognosis. Despite advances in systemic therapy, the incidence of BCBrM is rising due to prolonged survival of patients with advanced breast cancer, yet effective brain-targeted strategies remain scarce, underscoring a critical research gap. This review integrates recent mechanistic insights that illuminate the complex biology underpinning BCBrM and explores how these discoveries are driving therapeutic innovation. We detail the metastatic cascade from local invasion to brain colonization, and examine key signaling pathways orchestrating brain-specific metastasis. Emphasis is placed on the dynamic crosstalk between tumor cells and the brain microenvironment, including astrocytes, microglia, and neurons, as well as metabolic reprogramming and immune evasion. We critically evaluate current preclinical models and their translational relevance, highlighting recent advances in humanized and imaging-based systems. Emerging therapies, such as central nervous system-penetrant kinase inhibitors, antibody–drug conjugates, and immunotherapies, are discussed alongside persistent challenges in drug delivery and resistance. Finally, we outline future directions, calling for cross-disciplinary collaboration and innovative clinical trial designs to personalize care and improve patient outcomes. Together, this review underscores the urgent need to bridge biology and therapy to transform the management of BCBrM.