Liquid biopsy and its applications in veterinary medicine – a review

Liquid biopsy is a diagnostic and prognostic tool already reported in several studies with human oncologic patients, and shows potential for application in veterinary oncology. However, liquid biopsy is not a widely known technique in veterinary medicine, and related research is sparse. Liquid biopsy is based on the analysis of blood samples for detection of various tumoral products in circulation. It is a non-invasive technique, and provides results in real time. Information obtained from liquid biopsies can complement the information obtained from the analysis of tissue biopsy. In this review of literature, we present the background principles of liquid biopsy, its methodology, and the tumoral products that can currently be detected with this tool. In addition to circulating tumor cells, liquid biopsies allow detection of nucleic acids, including tumor DNA, micro-RNA, messenger RNA and exosomes. We present the value of liquid biopsy as a diagnostic and prognostic tool, its predictive value in tumor progression and treatment success, and usefulness to assist treatment choice. We discuss its limitations, and the challenges to implement its use in a large scale.