Comparative Analysis of the Role of Prostate Specific Antigen Parameters in Clinical Practice

Abstract

Introduction: Serum prostate specific antigen at the cutoff levels of 4 ng/ml has low specificity for prostate cancer. We evaluated various PSA parameters (i.e., total PSA density [tPSAD], free PSA density [fPSAD], the ratio of free to total PSA [f/t ratio], and age-specific PSA) in terms of cancer diagnosis and reducing the number of negative results for prostatic biopsies. Materials and Methods: A series of 305 patients was studied. Serum tPSA and fPSA levels were measured. Prostate volume was measured with transrectal ultrasound, and sextant biopsies were performed. The f/t ratio, tPSAD, and fPSAD were calculated. Sensitivity and specificity were calculated for age-specific PSA. Receiver operating characteristic curve analysis was used to analyze the diagnostic performance of these PSA parameters. A subpopulation of patients with serum PSA levels between 4 and 10 ng/ml also was analyzed with a specific view to reducing negative results of biopsies. The Mann-Whitney U test was used to analyze the difference in these parameters between patients with benign and malignant histologies. Results: There was significant difference in these PSA parameters between patients with benign and malignant histologies (p < 0.05). tPSAD had the largest area under the curve for total population as well as for patients with tPSA levels between 4 and 10 ng/ml. Although the f/t ratio had a larger area under the curve than did tPSA assay in patients with PSA levels between 4 and 10 ng/ml, the difference was not statistically significant. Using a tPSAD of 0.12 ng/ml/ml as the cutoff level of negative results of prostate biopsies could be reduced by 37% in patients with PSA levels between 4 and 10 ng/ml. Although the f/t ratio could reduce negative results of biopsies by 33.8% at the cutoff value of 0.26, 15.6% of cancers would be missed. Age-specific PSA could reduce 31% of negative prostatic biopsies, but 28% of cancers would be missed. Using combined tPSAD and the f/t ratio did not improve reductions of negative biopsy results. Conclusion: tPSA density has the highest sensitivity and specificity in differentiating benign from malignant prostates. By using tPSA density, negative results of prostate biopsies can be reduced by 37%, while missing only a small number of cancers.