Comparison of Prostate-Specific Antigen Adjusted for Transition Zone Volume Versus Prostate-Specific Antigen Density in Predicting Prostate Cancer by Transrectal Ultrasonography

Objective. Prostate-specific antigen is an excellent tumor marker, but it is not specific for prostate cancer. We evaluated the efficacy of prostate-specific antigen adjusted for transition zone volume calculated by transrectal ultrasonography in predicting prostate cancer in men with intermediate prostate-specific antigen levels of 4.1 to 10.0 ng/mL compared with prostate-specific antigen density. Methods. Between June 1998 and December 2001, prostate-specific antigen adjusted for transition zone volume was obtained from 131 patients who underwent ultrasonographically guided biopsies and had prostate-specific antigen of 4.1 to 10.0 ng/mL. Prostate-specific antigen density was calculated by dividing total serum prostate-specific antigen by total prostate volume, and total serum prostate-specific antigen was divided by transition zone volume to yield prostate-specific antigen adjusted for transition zone volume. This was compared with prostate-specific antigen density via receiver operating characteristic curves. Results. Of 131 patients, 34 (26%) had prostate cancer, and 97 (74%) had benign prostatic hyperplasia on pathologic examination. Total prostate volume was correlated with transition zone volume (P < .001). Mean prostate-specific antigen adjusted for transition zone volume and prostate-specific antigen density were 0.71 ± 0.25 and 0.27 ± 0.09 ng · mL^-1 · mL ^-1 in patients with prostate cancer and 0.32 ± 0.09 and 0.16 ± 0.05 ng · mL^-1 · mL^-1 in patients with benign prostatic hyperplasia. With a cutoff value of 0.35 ng · mL^-1 · mL^-1, prostate-specific antigen adjusted for transition zone volume had sensitivity of 82% and specificity of 84%. Receiver operating characteristic curve analysis showed that prostate-specific antigen adjusted for transition zone volume predicted biopsy outcome significantly better than prostate-specific antigen density (P < .05). Conclusions. Prostate-specific antigen adjusted for transition zone volume is more accurate than prostate-specific antigen density in distinguishing prostate cancer from benign prostatic hyperplasia in men with intermediate serum prostate-specific antigen of 4.1 to 10.0 ng/mL. Determination of transition zone volume by transrectal ultrasonography may be helpful for predicting the probability of positive biopsy results.