Background: The objective of this study was to evaluate the clinical significance of measuring the free-to-total (f/t) prostate-specific antigen (PSA) ratio for the differentiation of prostate cancer from benign prostatic hypertrophy (BPH) and for the staging of prostate cancer in Japanese men.
Methods: Before treatment, tPSA and fPSA were measured in 147 patients with prostate cancer and in 253 with BPH, using immunofluorometric techniques. Furthermore, the f/t PSA ratio and the tPSA density of the whole prostate (PSAD) were calculated.
Results: The tPSA and PSAD levels in patients with prostate cancer paralleled the clinical stage, and were significantly higher than the levels in patients with BPH, while the f/t PSA ratio was not associated with clinical stage, despite the significantly lower values in prostate cancer patients than in BPH patients. Furthermore, the tPSA and PSAD values, but not the f/t PSA ratio, were significantly different between patients with pathologically extraprostatic disease and those with organ-confined disease. Calculation of the specificity of each assay within the range of 80%-95% sensitivity showed that tPSA and PSAD provided better specificities than the f/t PSA ratio. However, there was no significant difference in specificities among these three assays. In prostate cancer and BPH patients with PSA values of 4.1-10 ng/ml, the specificities of tPSA and PSAD were also superior to that of the f/t PSA ratio.
Conclusion: These findings suggest that measurement of the f/t PSA ratio does not provide any significant additional information for the diagnosis and staging of prostate cancer in Japanese men when tPSA and PSAD values are available.