Prostate-specific antigen density.

Nearly 20 years have passed since PSA was definitively identified. Throughout this period, its clinical application as a tumor marker has expanded significantly. Today, besides monitoring prostate cancer therapy, PSA is being used extensively in mass screening programs for early detection of adenocarcinoma of the prostate and has become the most important tumor marker in urologic oncology. Although of unquestionable importance, PSA is not the perfect marker because of its lack of efficacy in discriminating BPH from prostate cancer. In order to enhance its sensibility, specificity, and predictive value, a series of variables influencing PSA levels have been studied and new parameters developed to correct discrepancies or confounding factors. Recognition of the relationship between PSA, prostate volume, and their interference with serum PSA levels made possible the development of the PSAD concept. Its wide application in different sets of patients for diagnostic and staging purposes resulted in enough data to demonstrate its usefulness and cost effectiveness as a second-line screening parameter, helping to distinguish BPH from prostate cancer in patients with PSA levels in the intermediate area, and avoiding some unnecessary biopsies. Even though PSAD does not offer a definitive solution for prostate cancer screening or management, its association with all the other diagnostic methods may offer the best way to assess the population at risk and assure their well-being (Fig. 5).