Dormancy and Recurrence in Breast Cancer Bone Metastasis: From Mechanisms to Clinical Translation.

Breast cancer bone metastasis often involves a prolonged dormancy phase, during which disseminated tumor cells (DTCs) remain undetectable and resistant to conventional therapies, posing a significant risk for late recurrence. Understanding the underlying mechanisms of tumor dormancy and reactivation is crucial for developing effective clinical interventions. However, current clinical translation faces multiple challenges, including limitations in detecting dormant tumor cells, insufficient biomarkers for dormancy, and difficulties in targeted drug delivery. Recent advances in elucidating the mechanisms of dormancy-such as the establishment of the pre-metastatic niche, intercellular communication in the bone marrow microenvironment, and signaling pathways regulating dormancy and reactivation-have provided novel therapeutic targets. Based on these mechanistic insights, nanotechnology-based drug delivery systems have emerged as promising strategies to precisely target dormant breast cancer cells in bone marrow niches. In this review, we summarize the current understanding of dormancy mechanisms in breast cancer bone metastasis, discuss the barriers hindering clinical translation, and highlight how mechanism-driven nanotherapeutic strategies may offer new opportunities to prevent recurrence by targeting dormant tumor cells.