Prostate-specific antigen corrected for prostate volume improves differentiation of benign prostatic hyperplasia and organ-confined prostatic cancer.

OBJECTIVE

To determine whether the ratio of PSA and prostate volume provides additional useful information for the discrimination of benign prostatic hyperplasia from prostatic carcinoma.

PATIENTS AND METHODS

Since 1989, a prospective study has been in progress involving 229 patients (49 with locally confined prostatic carcinoma, 180 with benign prostatic hyperplasia) to establish whether the ratio of prostate-specific antigen (PSA) and prostate volume, determined by transrectal ultrasound (longitudinal x anterior-posterior x transverse diameter x 0.52), allows a better differentiation than the absolute PSA values.

RESULTS

In this population of patients with prostatic disease, the positive predictive value for diagnosis of a prostatic carcinoma was 26% with an absolute PSA threshold value of 4.0 ng/ml, and 36% at a threshold value of 10 ng/ml. With a threshold value of the PSA/prostate volume ratio of 0.25 ng/(ml x cm3), the positive predictive value was 56% compared with 93% for a threshold value of 0.4 ng/(ml x cm3).

CONCLUSION

The ratio PSA/prostate volume is a superior method for the diagnosis of prostatic carcinoma both with regard to its sensitivity and its specificity in patients with absolute PSA values in excess of 4 ng/ml.