PROSTATE-SPECIFIC ANTIGEN DENSITY OF THE TRANSITION ZONE FOR PREDICTING PATHOLOGICAL STAGE OF LOCALIZED PROSTATE-CANCER IN PATIENTS WITH SERUM PROSTATE-SPECIFIC ANTIGEN LESS-THAN 10 NG. ML/

Purpose: Prostate specific antigen (PSA) density of the transition zon e, which is the density of serum PSA related to the volume of the tran sition zone; has been recently demonstrated to enhance prostate cancer prediction in patients with intermediate PSA levels. We further inves tigated the usefulness of PSA-transition zone for predicting extrapros tatic extension in clinically localized prostate cancer. Materials and Methods: Measuring the transition zone of the prostate by ultrasound using the prolate ellipsoid method, PSA-transition zone values were ca lculated prospectively in 198 patients with clinically localized prost ate cancers and serum PSA less than 10.0 ng./ml. who underwent radical retropubic prostatectomy. The ability of PSA-transition zone to predi ct extracapsular disease in the surgical specimen was compared to Glea son score, serum PSA, PSA density of the total prostate and percent fr ee PSA using univariate or multivariate analysis as well as receiver o perating characteristics curves. Results: A total of 104 patients (52. 5%) had pathologically organ confined prostate cancer while 94 of 198 (47.5) had extracapsular disease. PSA-transition zone levels were sign ificantly higher in extracapsular disease than organ confined cancers (0.84 versus 0.42 ng./ml./cc, p < 0.00001). Using multivariate analyse s PSA-transition zone and Gleason score were the most significant pred ictors of extracapsular disease. The area under the curve was larger f or PSA-transition zone (0.825) than any other parameter (p <0.004 vers us PSA density and p <0.001 versus PSA, percent free PSA or Gleason sc ore). A cutoff of 1.00 ng./ml./cc for PSA-transition zone provided 95. 1% specificity and 28.8% sensitivity for predicting extracapsular dise ase. Probability plots using the best combination of independent varia bles for predicting extraprostatic extension were developed. Conclusio ns: These data demonstrate that the use of the PSA-transition zone may be of additional value for indicating which patients with clinically localized prostate cancer and PSA less than 10.0 ng./ml. are at high r isk for extracapsular disease.