Diagnostic properties of percent-free PSA as a predictor of prostate cancer in Thai men with total serum PSA level of 4-10 ng/ml

Abstract

Objective: The percent-free prostate specific antigen (%fPSA) could enhance total PSA (tPSA) with regards to early prostate cancer detection by increasing its specificity. However, due to significant physiologic differences across races, the optimal cut-off level for %fPSA may vary. We aimed to determine optimal %fPSA cut-off level for Thai men aged between 50 to 80 years whose tPSA score ranged from 4-10 ng/mL and to evaluate its corresponding diagnostic properties, specifically sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The secondary endpoint is the relationship between Gleason Grade Group and %fPSA value. Materials and Methods: A total of 184 male patients from age 50-80 years whose tPSA was between 4-10 ng/ml were enrolled onto the study. Their %fPSA were measured before undergoing transrectal ultrasonography (TRUS) guided prostate biopsy, which procured at least 10 cores. All histologic reports were reviewed and confirmed for further analysis. Results: Out of the 184 patients registered the final diagnoses were 31 (16.84%) were positive for prostate cancer and the other 153 (83.16%) had benign prostate hypertrophy (BPH). At %fPSA cut-off of ≤ 10%, the sensitivity would be 22.6%, specificity 95.4%, PPV 50.0% and NPV 85.9%. However, at a %fPSA cut-off of ≤ 20%, the sensitivity was 77.4%, specificity 32.7%, PPV 18.9%, and NPV 87.7%. The %fPSA value has a direct relationship with sensitivity and NPV whereas it is inversely proportional to specificity and PPV. Lower %fPSA is associated with higher risk of prostate cancer. The area under the curve (AUC) of ROC curve was 0.65. The incidence of prostate cancer among patients with Gleason Grade Groups 1, 2, 3, 4, and 5 were 41.94%, 32.26%, 16.13%, 6.45%, and 3.23% respectively. The mean %fPSA scores among those groups were 14.75%, 17.64%, 10.19% ,13.33%, and 15.65% respectively. Conclusion: The decision to undergo prostate biopsy in Thai males with a tPSA score between 4-10 ng/ml can be guided by %fPSA, which proved to be an effective and useful predictive tool. The cut-off level of %fPSA ≤ 20% had the highest diagnostic properties in Thai men in our study which yielded a sensitivity of 77.4%, specificity of 32.7%, PPV of 18.9%, and NPV 87.7%. If %fPSA was ≥ 30%, there was no risk of prostate cancer in this cohort. In addition, with regard to disease severity, we found that %fPSA level is not associated with the Gleason Grade Grouping.