The role of serologic biomarkers “liquid biopsy” in the fight against breast cancer: From biological foundations to clinical impact

Abstract

Summary Liquid biopsy, analyzing circulating tumor-derived components, including ctDNA, circulating tumor cells, microRNAs, and exosomes, has emerged as a key tool in precision oncology. This review synthesizes evidence from the past five years, covering biological mechanisms, analytical platforms, clinical applications, and implementation barriers. Evidence from multiple clinical studies suggests ctDNA shows higher sensitivity for metastatic disease monitoring than conventional biomarkers such as CA15-3 and circulating tumor cells. For minimal residual disease detection, tumor-informed assays demonstrate sensitivity of 88%–100% and provide a median lead time of 8–15 months before clinical relapse. Despite these advances, early-stage cancer detection remains suboptimal, cost-effectiveness evidence is limited, and disparities in access are increasing. We critically evaluate current technologies and translational gaps and highlight the need for standardized clinical integration pathways. Overall, liquid biopsy is transitioning from a complementary diagnostic tool toward a longitudinal framework for cancer management, although substantial methodological and systemic challenges remain.