Background: For screening prostate cancer (CAP) using prostate-specific antigen (PSA), the indications of biopsies for patients showing slightly elevated PSA values are still controversial. Furthermore, the dependence of total PSA, free-to-total PSA ratio (F/T) and PSA density (PSAD) on prostatic volume in gray zone cases is unclear.
Methods: By analyzing 1913 patients with a serum total PSA ranging from 2.0 to 20 ng/ml, we evaluated the correlation between total PSA and age or prostatic volume and positive predictive value (PPV) in each range for total PSA, age and prostatic volume. Then suitable reference values for total PSA, F/T and PSAD were decided according to prostatic volume.
Results: There was no close correlation between PSA and age or volume. The PPV was high in the group with a prostatic volume of 10-30 ml. Prostatic volume was categorized into three groups, <20, 20-40 and > or =40 ml, and reference values for obtaining a sensitivity of 90% were proposed. The reference values of total PSA and PSAD were lowered and that of F/T was raised with increase in prostatic volume. The specificity was very low for the > or =40 ml group. The highest specificity of 36% in PSAD was obtained for the <20 ml group.
Conclusion: The reference values for total PSA, F/T and PSAD must be changed according to prostatic volume in order to maintain a sufficient diagnostic sensitivity of CAP. Of these parameters, PSAD showed a high specificity in the group with a prostatic volume of <40 ml.