Serum prostate-specific antigen as a predictor of prostate volume in men with benign prostatic hyperplasia

Objectives. To assess the utility of prostate-specific antigen (PSA) as a p redictor of prostate volume by characterizing the relationship between pros tate volume and serum PSA in men with symptomatic benign prostatic hyperpla sia (BPH) and no evidence of prostate cancer, stratified by decade of life. Methods. Placebo-controlled multicenter trials in patients with BPH and a s afety study in normal young men provided baseline measurements of serum PSA and prostate volume. The analyses included patients with a baseline prosta te volume measured by either transrectal ultrasound (TRUS) or magnetic reso nance imaging and baseline serum PSA. A common central laboratory was used for all but one of the individual studies; both laboratories used the Hybri tech method. Patients 80 years of age or older were excluded. Patients with a baseline serum PSA greater than 10 ng/mL were excluded to reduce the lik elihood of including occult prostate cancer cases. The patients in the BPH trials were screened at baseline by digital rectal examination (DRE) and se rum PSA. Those with suspicious findings underwent TRUS-guided biopsy; only patients with negative biopsies are included in these analyses. Results. The analyses included 4627 patients, 4448 from the BPH trials and 179 from the safety study. The men in the BPH trials were older (mean age /- SE, 63.7 +/- 0.10 years) than the men in the safety study (mean age +/- SE, 30.8 +/- 0.43), had larger prostates (mean volume +/- SE, 43.7 +/- 0.38 mt versus 26.3 +/- 0.49 mt in the safety study), and had higher serum PSA values (mean +/- SE, 2.6 +/- 0.03 ng/mL versus 0.7 +/- 0.39 ng/mL in the sa fety study). The relationship between prostate volume and serum PSA was eva luated using only the BPH trial data. Prostate volume and serum PSA have an age-dependent log-linear relationship (ie, their logarithms are linearly r elated, and the parameters of the relationship depend on age). Older men te nd to have a steeper rate of increase in prostate volume with increasing se rum PSA (P < 0.001 for differences between slopes), and there was a slight tendency for PSA density to increase with age. Receiver operating character istic (ROC) curves were constructed to evaluate the ability of serum PSA to predict threshold prostate sizes in men with BPH. The ROC curve analyses r evealed that PSA had good predictive value for assessing prostate volume, w ith areas under the curve ranging from 0.76 to 0.78 for various prostate vo lume cutoff points (30, 40, and 50 mt). Conclusions. Prostate volume is strongly related to serum PSA in men with B PH and no evidence of prostate cancer, and the relationship depends on age. Since treatment outcome or risk of long-term complications depend on basel ine prostate volume, serum PSA can estimate the degree of prostate enlargem ent sufficiently accurately to be useful for therapeutic decision making. T o achieve a specificity of 70% while maintaining a sensitivity between 65% and 70%, approximate age-specific criteria for detecting men with prostate glands exceeding 40 mt are PSA >1.6 ng/mL, >2.0 ng/mL, and >2.3 ng/mL for m en with BPH in their 50s, 60s, and 70s, respectively. (C) 1999, Elsevier Sc ience Inc. All rights reserved.