Recent advances in systemic treatment for HER2-negative breast cancer with brain metastases.

Human epidermal growth factor receptor 2 (HER2) -negative breast cancer brain metastases (BCBM) and leptomeningeal disease (LMD) pose significant clinical challenges due to limited treatment options and poor prognosis. Unlike HER2-positive BCBM, which has established therapeutic protocols, HER2-negative BCBM and LMD lacks standardized approaches. Recent advances have introduced novel systemic therapies targeting diverse pathways, including cell cycle regulation, DNA repair, immune modulation, vascular suppression, and leptomeningeal penetration, with emerging data supporting activity in LMD. Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors show promise in hormone receptor-positive subsets, particularly when combined with radiotherapy. Antibody-drug conjugates (ADCs), such as trastuzumab deruxtecan and sacituzumab govitecan, demonstrate enhanced central nervous system penetration and tumor-specific cytotoxicity, improving outcomes in both stable and active brain metastases. Immune checkpoint inhibitors (ICIs) and poly (ADP-ribose) polymerase (PARP) inhibitors also exhibit potential, though their efficacy varies by molecular subtype. Additionally, intrathecal therapies have become a cornerstone for LMD management, bypassing the blood-CSF barrier. Emerging therapies like selective estrogen receptor degraders (SERDs) and kinase inhibitors address resistance mechanisms, offering new avenues for personalized treatment. This review underscores the need for survival-prolonging, quality-of-life-preserving strategies with optimized safety profiles, highlighting the evolving landscape of HER2-negative BCBM and LMD management.