Prospective use of free prostate-specific antigen to avoid repeat prostate biopsies in men with elevated total prostate-specific antigen.

ABSTRACT

OBJECTIVES: We prospectively evaluated whether free PSA improves the specificity of PSA and can be useful as a clinical guide to avoid repeat prostate biopsies in patients with persistent PSA elevations, normal digital rectal examinations, and previous negative prostate biopsies. METHODS: Sixty-seven men with persistent PSA elevations (median 9.5, range 4.1-24.8 ng/mL), normal digital rectal examinations and two or more prior sextant biopsies (mean 2.8) had serum collected for measurement of total and free PSA. All patients were rebiopsied to determine the receiver operating characteristics of total PSA versus percent free PSA for prostate cancer detection. RESULTS: The study biopsy identified 11 prostate cancer cases. The median percent free PSA was significantly higher at 18.0% among men without prostate cancer compared to 6.7% in men with prostate cancer (P < 0.00005). When sensitivity was plotted against 1-specificity, the area under the receiver operating characteristic curve for percent free PSA was 0.93, compared to 0.69 for free PSA density, 0.66 for PSA density, and 0.51 for PSA. In patients with elevated total PSA levels, normal digital rectal examinations and two prior negative sets of sextant prostate biopsies, a cutoff of 10% free PSA would maintain sensitivity at 91% with a corresponding specificity of 86%. CONCLUSIONS: Selective measurement of percent free PSA can significantly improve the specificity of prostate cancer screening with PSA. A low percent free PSA (< 10%) appears to be a powerful predictor of prostate cancer even after two negative prostate biopsies.