Percentage of Free Prostate-specific Antigen: Implications in Modern Extended Scheme Prostate Biopsy

OBJECTIVES To validate the performance of percentage of free prostate-specific antigen (%fPSA) in men undergoing extended scheme biopsy. The current cutoff values for %fPSA were chosen using data from sextant biopsies, which have been known to miss a significant number of prostate cancer cases. Additionally, we sought to validate the use of %fPSA in men with a total PSA < 4.0 ng/mL or > 10.0 ng/mL. METHODS We evaluated %fPSA performance in 1077 men who had undergone initial extended prostate biopsy. The men were categorized according to their PSA level into 2 groups (> 4.0 and < 4.0) ng/mL. RESULTS The overall cancer detection rate was 42.1%. The mean PSA level was 7.6 ng/mL, and the mean %fPSA was 18.0%. The area under the curve for %fPSA was 0.59 (95% confidence interval 0.57-0.61) for all PSA levels, comparable to previous reports from sextant biopsy series. The performance of %fPSA in predicting prostate cancer on initial extended biopsy was improved with a PSA level of <= 4.0 ng/mL (area under the curve 0.66, 95% confidence interval 0.62-0.70) compared with a PSA level > 4.0 ng/mL (area under the curve 0.57, 95% confidence interval 0.55-0.59; P < .001). A specificity of 85% was achieved for a %fPSA cutoff of 11% for the <= 4.0-ng/mL group and 10% for the > 4.0-ng/mL group. CONCLUSIONS The performance of %fPSA in predicting the presence of prostate cancer was not altered when an extended biopsy scheme was used. Although a %fPSA level greater than our cutoffs would not rule out prostate cancer, a low %fPSA would be particularly useful in predicting prostate cancer, especially in men with normal digital rectal examination findings and a PSA level < 4 ng/mL. UROLOGY 77: 899-904, 2011. (c) 2011 Elsevier Inc.