Effect of finasteride on prostate-specific antigen density.

Objective: Prostate-specific antigen density (PSAD) has been proposed as a diagnostic marker for prostate cancer. Because treatment with finasteride may affect PSAD differently in men with BPH compared with men with BPH plus prostate cancer, we evaluated the diagnostic utility of PSAD in men treated with finasteride for twelve months.
Methods: Data for this analysis were obtained from 895 men with BPH enrolled in a twelve-month placebo-controlled North American study. Prostate volume was measured by magnetic resonance imaging and PSA was measured by the Hybritech immunoradiometric assay.
Results: Treatment with finasteride for twelve months increased the positive predictive value of PSAD for identifying the presence of prostate cancer from 14 percent to 30 percent. Using PSA values alone with a cutoff of 10 ng/mL at baseline and 5 ng/mL after twelve months of treatment, similar specificity and sensitivity could be achieved.
Conclusion: The data suggest that adjustment of PSA values during treatment with finasteride can be used to maintain the diagnostic accuracy for prostate cancer while PSAD can be used to provide additional reassurance without requiring adjustment for treatment.