PROSTATIC VOLUME AND RATIO OF FREE-TO-TOTAL PROSTATE-SPECIFIC ANTIGENIN PATIENTS WITH PROSTATIC-CANCER OR BENIGN PROSTATIC HYPERPLASIA

Purpose: We correlated prostatic volume with the ratio of free-to-tota l prostate specific antigen (PSA) in serum from patients with prostati c cancer or benign prostatic hyperplasia (BPH) to evaluate how prostat ic volume influences the ratio. Materials and Methods: We evaluated se ra from 395 patients (mean age 65 years, range 45 to 88) with prostate cancer (239) or BPH (156) for total PSA, free PSA and ratio of free-t o-total PSA. For detection of total and free PSA we used an Immulite free and total PSA assay. Prostatic volume was determined With transre ctal ultrasonography. Prostatic volume in BPH and prostate cancer pati ents was divided into 10 ml. groups, and mean ratio of free-to-total P SA was calculated for each volume group and both diseases. For statist ical analysis Mann-Whitney U and Kruskal-Wallis tests were performed i n addition to calculation of sensitivity and specificity, and receiver operator curves for prostates 60 ml. or less and greater than 60 ml. Results: For BPH patients the mean ratio of free-to-total PSA was 14.6 4 to 25.14% without a close relation to prostatic volume. In prostate cancer patients a proportional increase from 8.45 to 19.37% in the rat io of free-to-total PSA with volume was found. Mann-Whitney U analysis revealed significant differences in prostate cancer versus BPH only i n patients with prostates of 60 ml. or smaller (p = 0.0008 to 0.029). No significant differences were seen when prostate cancer and BPH pati ents with prostates larger than 60 ml. were compared (p = 0.082 to 0.8 68). Kruskal-Wallis test confirmed independence of the ratio of free-t o-total PSA from prostatic volume in BPH patients (p = 0.285) but depe ndence in prostate cancer patients (p < 0.0001). Sensitivity was highe r in patients with prostates 60 ml. or smaller (86.72%) than in patien ts with prostates larger than 60 ml. (66%), and specificity was lower at 45.78 and 56.16%, respectively. Conclusions: We have shown that the ratio of free-to-total PSA is influenced by prostatic volume in patie nts with prostate cancer. The ratio of free-to-total PSA provides usef ul information for differentiate BPH from prostate cancer in patients with small prostates but it is less useful in patients with larger pro states, probably because of the larger proportion of benign hypertroph ic tissue.