A new chapter in precision medicine: Circulating tumor cells in breast cancer prognosis and treatment.

Breast cancer (BC) persists as a leading cause of cancer-related mortality among women globally. While the characterization of molecular subtypes has improved our understanding and precision treatment of the disease, the detection and analysis of circulating tumor cells (CTCs) offer a complementary, dynamic perspective. Shed from primary tumors or metastatic sites, CTCs function as pro-metastatic precursors, providing critical insights into tumor progression, metastatic potential, and therapeutic response. We synthesize findings from key clinical trials that underscore the utility of CTCs in early diagnosis, prognostic assessment, and real-time treatment monitoring. Furthermore, we explore the potential of CTCs in uncovering novel biomarkers of therapy resistance and their emerging role in drug development. Ultimately, the integration of CTC-based liquid biopsies into clinical practice promises to open new avenues for precision medicine in BC.