[Liquid biopsy in tumor diagnostics : Applications, perspectives, and limitations of the "cancer liquidome"]

The detection of tumor-specific genetic alterations in body fluids as an addition to or even replacement for established tissue-based tumor diagnostics is currently a hot topic in academic research and industry. Progress in methods for nucleic acid analyses together with promising results from clinical studies have raised great expectations for cancer screening, diagnosis, prognosis, and therapy monitoring by means of a minimally invasive blood draw. Individual focused assays have already been introduced into routine diagnostics and represent a valuable option in cases where no tissue samples are available. However, before the use of liquid biopsy outside of clinical studies is enforced and more complex markers (like tumor mutational burden) are analyzed, several practical challenges and principal problems have to be addressed. This review focusses on the detection of free-circulating nucleic acids in blood plasma and critically discusses established and future applications as well as challenges and limitations of this new method.