Circulating cell-free DNA: a powerful biomarker for tumor management and a possible monitor tool in other pathological conditions.

‘Liquid biopsy’, i.e. the analysis of cfDNA in blood or body fluids, can give a live, ‘total’ image representing the entire heterogeneity of the system. The application of high throughput analytical procedures, such NGS or ddPCR, are necessary to obtain reliable data on such a small amount of starting material. Only few applications have achieved a clinical validation, due to the great variability in preanalytical procedures. In our work we evaluated cfDNA with three different aims. • Presence of mutation in a panel of 16 genes of the HR pathway in genomic and cfDNA in patients affected by breast cancer. We observed mutations in 3 out of 6 samples; in one case variant fraction in cfDNA was higer than in genomic DNA, probably due to limited ability to detect clonal heterogeneity in tissue. • Monitoring tool for determining septic risk in patients undergoing dialysis. We detected in a sample, in accordance with the emoculture, a Staphylococcus strain together with Propionibacterium and Streptococcus strains. The detection of Burkholderia multivorans in another sample raised the possibility to identify those bacteria that take more than the canonical 5 days of emoculture to growth, or that completely do not grow in emoculture conditions. • Detection of donor-derived cfDNA in transplanted patients. We identified more than 50% of donor derived polymorphisms just after reperfusion, falling down to 10% one day after surgery and then disappearing. The possibility to cross our data with clinical parameters will help us to better describe the pertinence of our results to the effective status of patients. In all the three settings, we are collecting other samples to have a broader amount of data that will allow us to perform statistical analysis to effectively validate our procedures.