Specificity and accuracy of TRUS-measured PSA-density and transition zone-PSA in the diagnosis of prostate cancer

Between 4 and 15 ng/ml serum prostate-specific antigen (PSA) has a low specificity for prostate cancer (PCa). One accepted method to enhance this specificity is transrectal ultrasonography (TRUS)-measured PSA-density (PSA-D). We compared this method with a new alternative, transition zone PSA (PSA-TZ). We measured total and transition zone prostatic volumes by TRUS and calculated PSA-D and PSA-TZ in 59 patients with suspicion of PCa and PSA between 4 and 15 ng/ml. All patients then had sextant biopsies of the prostate, 30 were positive for PCa and 29 showed benign tissue. With a cut-off value of 0.35, PSA-TZ had a positive predicted value of 77% for PCa, whereas PSA-D, with a cut-off value of 0.12, had a positive predicted value of 55%. Our data suggest PSA-TZ to be more reliable for avoiding unnecessary biopsies in patients with PCa suspicion and serum PSA below 15 ng/ml. PSA-TZ, calculated by TRUS, enhances the specificity of PSA for needle biopsy diagnosis of PCa.