BACKGROUND.
The clinical value of prostate-specific antigen (PSA) density in differentiating between prostate cancer and benign prostatic hyperplasia has been the subject of several studies. In this context the question has been raised about the diagnostic benefit of PSA transition-zone density (PSA-TZ density = total PSA/transition-zone volume) in the detection of prostate cancer. In the following study the value of PSA-TZ density alone and in combination with free PSA was investigated. METHODS. Between August 1995-May 1996, 308 first-line screening volunteers with elevated total PSA levels ranging from 2.5-10.0 ng/ml were evaluated. All patients underwent digital rectal examination, transrectal ultrasound, and transrectal ultrasound-guided biopsy of the prostate. Prior to these investigations, serum was obtained and total as well as free PSA levels were obtained. PSA transition-zone density (PSA-TZ density) was defined as follows: PSA-TZ density = total PSA/transition-zone volume. RESULTS. ROC curve analyses for PSA-TZ density showed that by using a PSA-TZ density of more than 0.22 ng/ml/cc as a biopsy criterion, 24.4% of negative biopsies could be avoided; ROC curve analyses for free PSA showed that by using percent free PSA <20% as a biopsy criterion, 45.5% of negative biopsies could be eliminated. When combining these two diagnostic tests, 54.2% of negative biopsies could be avoided. CONCLUSIONS. We conclude that PSA-TZ density, in addition to total and free PSA, is a new opportunity which renders it possible to calculate the likelihood of detecting prostate cancer on repeat biopsies in an individual patient.