Effect of finasteride on free and total serum prostate‐specific antigen in men with benign prostatic hyperplasia

OBJECTIVE: To examine changes in the free-to-total (f/t) serum prostate-specific antigen (PSA) ratio among men treated with finasteride for benign prostatic hypertrophy. PATIENTS AND METHODS: Blood samples were taken from 20 men (mean age 71 years, range 61-87) before and after a minimum of 9 months of treatment with finasteride and the f/tPSA ratio determined using the Immulite assay system. RESULTS: Although mean total and free PSA levels decreased significantly, the mean f/tPSA ratio increased only slightly and not significantly; the ratios remained unchanged in men with an initially low or high (< > 10%) ratio. CONCLUSIONS: Concern has been expressed over the loss of the discriminatory power of serum PSA in a patient receiving treatment with finasteride. The f/tPSA ratio, currently used to help differentiate benign from malignant processes in the prostate, remains valid during treatment with finasteride; it does not affect the f/tPSA ratio.