Molecular forms of prostate-specific antigen in serum with concentrations of total prostate-specific antigen < 4 mu g/L: Are they useful tools for early detection and screening of prostate cancer?

Molecular forms of prostate-specific antigen (PSA) improve the differentiat ion between benign prostatic hyperplasia (BPH) and prostate cancer (PCa) in men with total PSA concentrations between 4 and 10 mug/l. To evaluate the diagnostic utility of free PSA (fPSA) and complexed PSA forms for identific ation of men with PCa in the low PSA range of <4 <mu>g/l, total PSA (tPSA), alpha (1)-antichymotrypsin complexed PSA (PSA-ACT) and fPSA (Roche Elecsys [ES] system) as well as tPSA and complexed PSA (cPSA) (Bayer Immuno I syst em) were measured in archival serum samples from 31 untreated patients with PCa, 66 patients with BPH, and 90 men without prostatic disease. The media n ratios of fPSA/tPSA, PSAACT/tPSA and cPSA/tPSA were significantly differe nt between patients with BPH and PCa (27.2 vs. 19.4%, 64 vs. 88%, 77.2 vs. 88.2%, p < 0.05). No associations between PSA forms and tumor stage and gra de were found. Analysis of the receiver operating characteristic curves sho wed that these ratios could discriminate better between BPH and PCa patient s than determination of the analytes tPSA, fPSA, cPSA and PSA-ACT alone. Th e use of one of the ratios would have eliminated roughly half of the unnece ssary biopsies in this study. The ratios should be considered as potential tools to increase the selectivity of PCa detection at low PSA concentration . The ratios fPSA/tPSA and cPSA/tPSA can be determined using commercially a vailable assays so that one of these ratios could be preferred instead of P SA-ACT determination. The ratios could be useful in assessing the risk of P Ca in the individual and therefore in deciding on prostate biopsy for final diagnosis. (C) 2001 Wiley-Liss, Inc.