Differential suppression of serum prostatic acid phosphatase and prostate-specific antigen by 5-alpha-reductase inhibitor.

Objective: To evaluate the effect of finasteride (Proscar) on the serum levels of prostatic acid phosphatase (PAP) and prostate-specific antigen (PSA) in patients with benign prostatic hyperplasia (BPH).

Patients And Methods: Thirty patients on finasteride therapy for BPH formed the study group. Serum PSA and PAP levels were monitored for 2 years while the patients were receiving finasteride.

Results: During 12 months of finasteride therapy the serum PSA was suppressed but serum PAP was unaffected. The baseline mean PAP value was 1.303 ng/mL prior to finasteride therapy; this changed to 1.510 ng/mL (P = 0.195) at 6 months and 1.166 ng/mL (P = 0.383) at 12 months. The serum PSA was 2.630 ng/mL at baseline, 1.757 ng/mL (P < 0.001) at 6 months and 1.545 ng/mL (P = 0.001) at 12 months.

Conclusions: Further studies are warranted to determine if PAP has a role as a tumour marker in patients whose PSA is suppressed as a result of finasteride therapy.