Circulating tumor cells in breast cancer bone metastasis: mechanisms, clinical relevance, and future directions

Circulating tumor cells (CTCs) play a critical role in the metastatic cascade and have emerged as promising biomarkers for cancer diagnosis, prognosis, and therapeutic monitoring. In breast cancer, CTCs mediate bone metastasis through intricate interactions with the bone microenvironment, regulating process such as homing, dormancy, reactivation, and colonization. Advances in CTC detection and characterization have deepened our understanding of their physical and biological properties, yet significant technical and biological challenges remain. This review provides a comprehensive overview of the roles of CTCs in breast cancer bone metastasis and highlighting their clinical significance, current limitations, and future applications.