The presence of small amounts of circulating DNA in plasma was demonstrated 60 years ago. Since then, cell-free DNA has been tested for quantity, fragmentation pattern, and tumor-specific sequences in patients with various malignancies. Recent studies have shown that cell-free DNA levels are distinctly increased in most patients with prostate cancer (PCA) and that the DNA fragmentation pattern is different from healthy individuals and patients with benign prostate disease. The origin of this circulating DNA remains largely unknown, but it is established that a small fraction of the DNA is derived from the tumor itself, and genetic (allelic imbalances) and epigenetic (DNA methylation) alterations are regularly detected in patients with PCA. The detection of increased DNA levels and tumor-specific DNA sequences may provide diagnostic and prognostic information. The recent findings in the emerging field of cell-free DNA will be discussed.
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