Latest development of liquid biopsy

Liquid biopsy provides the opportunity of detecting and analyzing cancer in various body fluids. In peripheral blood, apart from circulating cell free DNA, circulating cancer cells and other tumor-associated compounds such as extracellular vesicles are also emerging candidates for detection. Compared to conventional tissue or cytology samples, liquid biopsy is non-invasive, safe, and easy to repeat. In view of tumor heterogeneity, it is also suggested that circulating cell free DNA may be more representative of the whole tumor cells population than a biopsy or cytology sample. In addition to assisting in the initial diagnosis, liquid biopsy can also be tailored for disease monitoring, detecting resistance mutation, tumor recurrence, and perhaps for screening in the future. The accuracy of this test is greatly facilitated by the advances of molecular techniques, from PCR-based methods, DNA sequencing, Digital PCR, to the more state-of-the-art next generation sequencing technologies. Despite the tremendous potential of liquid biopsy, there are limitations and not all clinical relevant cancer biomarkers can be detected in liquid biopsy at the present moment. The clinical utility of many of the tests derived from liquid biopsy required further investigations and clinical validation. This review provides an overview of the concept of liquid biopsy, its clinical applications, and discuss the multifaceted advances in this field.