MOLECULAR FORMS OF SERUM PROSTATE-SPECIFIC ANTIGEN : The Clinical Value of Percent Free Prostate-Specific Antigen - 11/09/11
Résumé |
Although prostate-specific antigen (PSA) is the most clinically useful tumor marker available for the diagnosis and management of prostate cancer,55 as currently used PSA testing is insufficiently sensitive and specific for prostate cancer to be considered the ideal tumor marker for early detection of the malignancy. An increased serum PSA level is not pathognomonic of prostate cancer; nor, conversely, do levels below the reference range necessarily indicate its absence. Other conditions, such as bacterial prostatitis, urinary retention, and benign prostatic hyperplasia (BPH) also may be associated with increased serum PSA levels.53, 81 To detect prostate cancer with reliability at an early stage, a low serum PSA cut-off level of 4 ng/mL is used during screening. Use of this low cut-off value, however, is associated with an appreciable risk of false-positive results, thus diminishing its predictive value and resulting in unnecessary biopsies for those with benign conditions. Approximately 25% to 30% of men with BPH and 80% with proven prostate cancer have serum PSA concentrations greater than 4 ng/mL.14, 17, 18, 81 Thus, about 20% of men with diagnosed prostate cancer have serum PSA concentrations below 4 ng/mL.17 Earlier studies showed 38% to 48% of patients with clinically significant organ-confined prostate cancer to have serum PSA levels within the standard reference range of 0 to 4 ng/mL.32, 37 Had the serum PSA level been the sole diagnostic criterion, these men would not have had their cancer diagnosed. The use of a PSA cut-off level of 4 ng/mL for screening is associated with a false-positive rate of 65% and a false-negative rate of 20% (i.e., false-negative results are obtained for men with suspicious findings at digital rectal examination).14, 17, 18 The techniques currently used in the immunodetection of serum PSA concentrations are of limited clinical value in the early detection of prostate cancer and its distinction from BPH.
In attempts to improve the clinical utility of serum PSA measurements, various concepts have been developed and evaluated, such as PSA density,7 PSA velocity,12, 56 and age-specific reference ranges.57 In addition, several investigations have shown that PSA exists in several molecular forms in serum and that the concentrations of these molecular forms vary according to the disease state of the gland.22, 44, 83 The major aim of this presentation is to provide a molecular basis for the occurrence of multiple molecular forms of PSA and the possibility of improving the clinical utility of PSA testing by specific measurements of these various forms of PSA.
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| Address reprint requests to Per-Anders Abrahamsson, MD, PhD, Department of Urology, University Hospital Lund, S-22185 Lund, Sweden This article is supported by grants from the Swedish Medical Research Council (project no. 7903); the Swedish Cancer Society (project no. 3555); the Faculty of Medicine at Lund University; the Research Fund and the Cancer Research Fund at the University Hospital, Malmö; the Crafoord Foundation; the Gunnar, Arvid, and Elisabeth Nilsson Foundation; the Foundation for Urology Research in Malmö; the Fundacion Frederico S.A.; and the Maud & Birger Gustavsson Foundation. |
Vol 24 - N° 2
P. 353-365 - mai 1997 Retour au numéro
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- AGE-SPECIFIC REFERENCE RANGES FOR SERUM PROSTATE-SPECIFIC ANTIGEN
- Thomas D. Richardson, Joseph E. Oesterling
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- Carl A. Olsson, Glen M. de Vries, Ralph Buttyan, Aaron E. Katz
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