A, a Bioanalyzer 2100 (Agilent Technologies) profile showing the length distribution of cfDNA isolated from a high-risk prostate cancer patient reported in ref. 31. The x-axis shows the size of DNA fragments (in base pairs); the y-axis, fluorescent intensity, proportional to DNA concentration. Note the unusual trimodal distribution of DNA sizes (150, 300, and 450 bp) most likely indicating a very high tumor burden. B, cfDNA concentration in blood of healthy subjects/nonmalignant patients (blue box) and in cancer patients (orange box) based on ref. 30. The left y-axis shows the cfDNA concentration on a logarithmic scale (in ng/mL of blood) and the right shows the number of diploid genome equivalents per mL of blood (assuming 6 pg of DNA per diploid genome).