Liquid biopsy: Cell-free DNA based analysis in breast cancer

Breast cancer management has witnessed significant advancements, especially in the diagnosis and treatment response monitoring through the implementation of imaging techniques and tissue biopsy procedures. Nevertheless, there is potential for further improvement by integrating less invasive approaches that offer timely and precise information. Liquid biopsy, which involves isolating tumor-derived components such as circulating cell-free DNA (cfDNA) and its subset known as circulating tumor DNA (ctDNA), can greatly enhance the prognosis, identification of specific genomic alterations, and selection of targeted therapies for breast cancer patients. While the incorporation of ctDNA-based testing into clinical practice has been primarily focused on metastatic breast cancer (MBC), there is growing interest in its applicability in early-stage breast cancer given the ability to capture tumor heterogeneity. Additionally, the minimally invasive nature of ctDNA testing allows for multiple serial samplings, providing a dynamic assessment of tumor characteristics and monitoring treatment response over time. However, the analysis of ctDNA in breast cancer encounters a significant challenge related to its abundance and the temporal aspect of the disease. The quantity of ctDNA in relation to the disease stage poses an important obstacle that often hinders its accurate analysis. Therefore, it is crucial to ensure timely sample collection, employ sensitive detection methods, and carefully manage the pre-analytical phase to overcome these challenges and facilitate successful ctDNA analysis in breast cancer. This article aims to summarize the methodologies employed in the detection of ctDNA, provide a comprehensive review of the current applications of ctDNA analysis in breast cancer, and elucidate the underlying rationale for its potential extension into broader clinical contexts. Furthermore, models that could facilitate the widespread adoption of ctDNA testing in various healthcare institutions are discussed.