Volume-specific cutoffs are necessary for reproducible application of prostate-specific antigen density of the transition zone in prostate cancer detection

Objectives. To determine the effect of prostate volume on the specificity o f prostate-specific antigen density (PSAD) and PSAD of the transition zone (PSA-TZ) in the detection of prostate cancer. Methods. Between February 1994 and April 1998, transrectal ultrasound-guide d prostate needle biopsies were performed in 235 men with serum prostate-sp ecific antigen (PSA) levels between 4.0 and 10.0 ng/mL. The PSAD and PSA-TZ specificities were calculated at 95% sensitivity cutoff levels generated f rom the whole group, as well as from cohorts stratified by transition zone index or prostate volume. Results. Statistical significance was noted between the benign (n = 176) an d prostate cancer (n = 59) groups for all tested PSA parameters. At 95% sen sitivity, PSA-TZ carried a specificity of 37.5% compared with 29.6% for PSA D. When applying a single 95% sensitivity cutoff derived from the entire gr oup to individual volume-stratified cohorts, the specificity decreased to 0 % in glands less than 30 g in size. A 95% sensitivity PSA-TZ cutoff generat ed individually for volume-stratified cohorts of glands less than 30, 30 to 40, and 40 to 60 g resulted in more consistent specificity of 28.2%, 35.2% , and 45.7% for each cohort, respectively. Conclusions. Unlike whole group-derived cutoffs, the use of volume-specific PSA-TZ cutoffs allows consistently high specificity in all volume-stratifi ed cohorts. The discrepancies in the PSA-TZ and PSAD specificities in publi shed reports are likely due to the application of published cutoffs to popu lations of differing prostate volumes. The use of volume-specific cutoffs r esults in reproducible specificity in populations with differing prostate v olume distribution, and thereby definitively resolves the differences in PS A-TZ specificity reported in published reports. UROLOGY 58: 222-227, 2001. ((C) 2001, Elsevier Science Inc.