Role of Cell‐Free Plasma DNA as a Diagnostic Marker for Prostate Cancer

Abstract: Recent evidence has shown elevated levels of cell‐free plasma DNA in cancer patients. The aim of the present study was to quantify and compare the levels of cell‐free plasma DNA in patients with prostate cancer, prostatic intraepithelial neoplasia (PIN), and benign prostatic hypertrophy (BPH) to examine if it offered a useful diagnostic test. Blood samples were obtained from 37 patients attending a clinic for prostate biopsies. Samples were taken prior to biopsy, within 1 hour of the biopsy, and then 2 weeks later. DNA was extracted using a QIAamp blood kit (Qiagen) and plasma DNA measured, in genome equivalents/milliliter plasma (GE/mL), using real‐time quantitative PCR for the β‐globin gene. Prior to biopsy, plasma DNA concentration in BPH patients was 936 GE/mL (median; range: 633–2074 GE/mL), while cancer and PIN patients had significantly higher levels of DNA at 1734 GE/mL (median; range: 351–3131 GE/mL; P= 0.01) and 1780 GE/mL (median; range: 1514‐2732 GE/mL; P= 0.04), respectively. Comparison of plasma DNA concentration before and after biopsy showed that 60 minutes after biopsy values were significantly higher in both BPH (1494 GE/mL; range: 613‐2522 GE/mL; P= 0.029) and cancer (2758; range: 1498‐5226 GE/mL; P= 0.007) patients. ROC analysis of the data indicated a sensitivity of 85% and a specificity of 73% when DNA concentration of 1000 GE/mL was taken as an indicator of malignancy or PIN. The data suggest that quantification of cell‐free plasma DNA may have an important diagnostic role in distinguishing benign and malignant prostate disease.