The role of the liquid biopsy as a clinical tool for early prediction in prostate cancer

The evolution of the liquid biopsy from a novel biomarker discovery platform to a clinical (molecular diagnostic) assay represents a true inflection point in the practice of medical (oncologic) pathology. Initially associated with the quantitation of breast cancer circulating tumor cells (CTCs) found in blood as a measure of tumor burden, the field quickly has expanded to include the isolation and capture of cell free/tumor DNA, exosomal RNA species and peptide-protein analytes in all body fluids including CSF and urine (1-4). The improvements in specimen handling, isolation techniques and the robust identification of low abundance nucleic acids have continued to advance the field; however, challenges persist as investigators attempt to understand the importance of rare variants in a complex setting of tumoral heterogeneity, drug resistance pathways and host-immune response. Recent success including the development of the first Food and Drug Administration (FDA) approved blood-based (liquid biopsy) companion diagnostic for the drug Tarceva (erlotinib) in patients with non-small cell lung cancer have further realized the potential (5). A simple, non-invasive, liquid biopsy approach for men with a suspicion of prostate cancer that offers insight into early detection of clinically significant disease while not over-diagnosing low-risk prostate cancer would have a critical impact on reducing the number of prostate needle biopsies and most importantly limiting over-treatment (6,7).