Liquid biopsy in breast carcinoma: Are we there yet?

Breast carcinoma is the most common malignancy among women worldwide. Liquid biopsy is a method of obtaining tumour-derived material from blood and body fluid. This includes the assessment of circulating tumour cells (CTCs), circulating tumour deoxyribose nucleic acid (ctDNA), tumour educated platelets (TEPs) and exosomes. Detection of CTCs and ctDNA in liquid biopsy has been shown to have prognostic and predictive value in both early and metastatic breast carcinoma. The study of CTCs could also advance our understanding of aspects of tumour biology, including epithelial mesenchymal transition. ctDNA can be used to assess and monitor the molecular profile of breast carcinoma. It may help detect new genetic alterations in tumours and predict disease progression before the onset of clinical features or radiological evidence. TEPs and exosomes are also emerging as diagnostic, prognostic and predictive markers of breast carcinoma. Thus, liquid biopsy provides a non-invasive, repeatable method for the dynamic assessment of the tumour. Many methods have been used for the detection of CTCs and ctDNA. Most of these are still in the research stage and only the CellSearch method for the detection of CTCs and Therascreen PIK3CA RGQ polymerase chain reaction (PCR) assay for the detection of PIK3CA (Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha) mutations in liquid biopsy have approval of the United States, Food and Drug Administration. However, their high costs, lack of standardized procedures, and a long and complicated detection process have limited their use. Despite its limitations, liquid biopsy is a useful tool in clinical decision making and has the potential to play an increasingly important role in the management of breast carcinoma in the future as we move toward more personalized cancer care.