Objectives. To define the clinical reason for the further refinement of stratification of prostate-specific antigen (PSA) outcome using percent positive prostate biopsies in intermediate-risk patients.

Methods. A chi-square metric was used to compare the distribution of pretreatment clinical and post-treatment pathologic factors for patients with intermediate-risk prostate cancer with 50% or less versus greater than 50% positive prostate biopsies. The PSA outcome stratified by the percent positive biopsies was calculated according to the Kaplan-Meier actuarial method. Comparisons of actuarial PSA failure-free survival were performed using the log-rank test.

Results. The group with greater than 50% positive biopsies for prostate cancer had a significantly higher proportion of patients with pretreatment PSA values greater than 10 to 20 ng/mL (P = 0.01), biopsy Gleason score 4+3 (P = 0.05), and 1992 American Joint Committee on Cancer clinical category T2b (P = 0.01) than did the group with less than 50% positive biopsies. The group with greater than 50% positive biopsies also had a significantly higher proportion of patients with prostatectomy Gleason score 4+3 or higher (P = 0.001), pathologic Stage T3b (P <0.0001), and rate of positive surgical margins (P = 0.002) than did the group of patients with less than 50% positive biopsies.

Conclusions. The results of this study provide an explanation on the basis of the pretreatment and post-treatment predictive factors for the difference in PSA outcome for intermediate-risk patients when stratified by the percent positive biopsies.