Harnessing cell-free DNA: plasma circulating tumour DNA for liquid biopsy in genitourinary cancers.

In the era of precision oncology, liquid biopsy techniques, especially the use of plasma circulating tumour DNA (ctDNA) analysis, represent a paradigm shift in the use of genomic biomarkers with considerable implications for clinical practice. Compared with tissue-based tumour DNA analysis, plasma ctDNA is more convenient to test, more readily accessible, faster to obtain and less invasive, minimizing procedure-related risks and offering the opportunity to perform serial monitoring. Additionally, genomic profiles of ctDNA have been shown to reflect tumour heterogeneity, which has important implications for the identification of resistant clones and selection of targeted therapy well before clinical and radiographic changes occur. Moreover, plasma ctDNA testing can also be applied to cancer screening, risk stratification and quantification of minimal residual disease. These features provide an unprecedented opportunity for early treatment of patients, improving the chances of treatment success. Liquid biopsy techniques, especially the use of plasma circulating tumour DNA (ctDNA) analysis, are a convenient, fast and non-invasive approach to the diagnosis and monitoring of urological cancers, and could enable selection of targeted therapy before clinical and radiographic changes occur. In this Review, the authors discuss the uses of liquid biopsy and plasma ctDNA analysis in particular, and consider how it could be used in clinical practice now and in the future.