Analysis of percent free prostate-specific antigen (PSA) for prostate cancer detection: influence of total PSA, prostate volume, and age

Abstract

Objectives: To determine whether the use of the free-to-total PSA ratio (percent free PSA) could increase the specificity of PSA testing for prostate cancer detection in men with serum PSA concentrations between 4.0 and 10.0 ng/mL, and to assess the influence of total PSA, prostate volume, and age on percent free PSA.

Methods: Sera were obtained from 217 men with histologically confirmed diagnoses (139 prostate cancer, 78 benign). Free and total PSA concentrations were determined using Hybritech Tandem assays.

Results: Use of percent free PSA increased PSA specificity: 29% of negative biopsies would be spared while retaining 95% sensitivity. Percent free PSA increased with increasing age and prostate volume. Percent free PSA decreased as total PSA increased. A significant relation exists between percent free PSA and the probability of a positive biopsy; in this cohort, a patient with a low percent free PSA (< or = 10%) had a higher probability of cancer (63 +/- 9%) than a patient with a high percent free PSA (> or = 26%) (probability 2 +/- 3%).

Conclusions: Percent free PSA may be used as an aid in distinguishing prostate cancer from benign disease in men with a total PSA between 4.0 and 10.0 ng/mL. Large prospective multicenter trials are required to develop consistent recommendations and determine the appropriate cutpoints and risk probabilities, controlling for total PSA, prostate volume, age, and biopsy history.