Circulating cell-free DNA in plasma of melanoma patients: qualitative and quantitative considerations.

DNA integrity in blood is an emerging biomarker in cancer. Here we report a real time PCR approach for the absolute quantification of four amplicons of 67, 180, 306 and 476 bp in cutaneous melanoma. Three different integrity indexes (180/67, 306/67 and 476/67 ratios) were tested for their ability to reflect differences in plasma cell-free DNA (cfDNA) fragmentation in 79 patients affected by cutaneous melanoma and 34 healthy subjects. All the three integrity indexes showed higher values in melanoma patients in comparison with healthy subjects. According to ROC curve analysis, the ratio 180/67 is the most suitable index to be used in cancer patient selection, even if the combination of the 3 indexes gives the best performance in terms of clinical sensitivity. The most represented fragments in plasma of melanoma patients are those comprised between 181 and 307 bp, while in healthy subjects there is a prevalence of shorter fragments (67-180 bp). In conclusion, DNA integrity indexes can be considered suitable parameters for monitoring cfDNA fragmentation in melanoma patients.