Percentage of Free PSA in Black versus White Men for Detection and Staging of Prostate Cancer: A Prospective Multicenter Clinical Trial
Reviewers: Li Liu, MD
Source: Urology, Volume 55:372-376, (March) 2000.
Précis: Free PSA percentage is effective for prostate cancer detection in black men.
Measurement of serum prostate-specific antigen (PSA) is widely used as an aid in the early detection of prostate cancer. Prostate-specific antigen exists in multiple forms in serum, both bound and free. For unknown reasons, the percentage of free PSA is lower in serum samples from patients with prostate cancer than in serum samples from patients with a normal prostate or benign disease. Low percentages of free PSA are well established as indicators of prostate cancer, but the difference between races has not been evaluated.
In this study, a total of 79 black and 647 white men were screened for prostate cancer. All subjects were between the ages of 50 and 75 years, with PSA concentrations between 4.0 and 10.0 ng/ml and nonsuspicious digital rectal examination findings. All men had undergone needle biopsy of the prostate.
- A lower percentage free PSA indicated a higher probability of prostate cancer and a higher percentage free PSA indicates a low probability of cancer for both races.
- At a free PSA cutoff of 25%, the sensitivity was 95% in both blacks and whites.
In this study, determination of the percentage of free PSA has the same sensitivity and specificity in detecting early prostate cancer in black men as in white men with the use of 25% free PSA as cutoff, unnecessary biopsies could have been avoided in approximately 25% of both white and black men. This result may not apply to men with PSA of < 4.0 or > 10.0 ng/ml.