Prospective Study of Quantitation of Plasma DNA Levels in the Diagnosis of Malignant versus Benign Prostate Disease

Purpose: The aim of this study was to determine the potential of cell-free DNA levels as a diagnostic marker for prostate cancer, having first established the effect that blood sample processing has on this measurement. Experimental Design: A total of 152 blood samples were collected prospectively from patients before their prostate biopsy and 25 from men in two distinct control groups. Blood was processed to yield three components: one-spin plasma ( n = 68), two-spin plasma ( n = 152), and serum ( n = 56 ) samples. Results: Having established the effect of sample preparation on the measured DNA level, the more reliable two-spin plasma sample was used to determine the relationship between DNA and the presence of prostate cancer. Those patients with cancer ( n = 78) had a significantly higher level of DNA compared with the control groups ( P < 0.0001 and P < 0.0001). However, DNA levels in patients with a benign biopsy ( n = 74) were significantly higher than the 78 patients confirmed to have cancer ( P = 0.02). Conclusions: We conclude that the sample type used in the quantitation of cell-free DNA has an effect on the level reported. Elevated levels are present in the two-spin plasma samples of patients with prostate cancer compared with healthy controls but are not of diagnostic value during the management of prostate cancer.