Background: The role of prostate-specific antigen (PSA) isoforms in the
detection of prostate cancer in a non-screened population in the UK remains to be
determined.
Methods: Consecutive patients undergoing diagnostic transrectal
ultrasound-guided biopsy of the prostate were studied. Prior to biopsy, a blood
sample was obtained and total, complexed and free PSA concentrations measured.
Results: Of the 171 patients included in the study, 103 were found to
have prostate cancer. There were significant differences in total and complexed PSA
concentrations and in the ratio of free-to-total PSA (all P
<0.001) between patients with prostate cancer and those with benign disease.
Receiver operating characteristics (ROC) curve analysis showed that the corresponding
areas under the curves were similar. Restricting the analysis to the 77 patients who
had total PSA concentrations between 2 and 10 µg/L, ROC curve analysis showed that
total and complexed PSA concentrations failed to discriminate between benign and
malignant disease. In contrast, the areas under the ROC curve were greater for the
free-to-total ratio (P = 0.033).
Conclusion: These results show that in patients with total PSA
concentrations between 2 and 10 µg/L, the free-to-total PSA ratio was superior to
total PSA concentration in discriminating between patients with benign and malignant
disease.
