The liquid biopsy: towards standardisation in preparation for prime time

The liquid biopsy holds potential as a more cost-effective, easier, less-invasive method for diagnosing and monitoring cancer, as well as predicting response to many currently available therapies. Circulating tumour cells (CTCs) and circulating free DNA (cfDNA) are currently the most intensely investigated analytes, with some tests already approved in clinical practice. Despite the potential of the liquid biopsy for managing patient therapy, there is currently no widely accepted consensus regarding pre-analytical blood sample handling and technologies used for extracting cfDNA and isolating CTCs, or optimum workflows for their molecular analyses – all of which are required before liquid biopsies can become routinely used in the clinic. Here, we discuss the current status of liquid biopsy testing in patients with solid tumours and the variation in blood sample handling and isolation/extraction methods, focusing on cfDNA and CTCs