BIOLOGIC VARIABILITY OF PROSTATE-SPECIFIC ANTIGEN AND ITS USEFULNESS AS A MARKER FOR PROSTATE-CANCER - EFFECTS OF FINASTERIDE

Objectives. The effects of finasteride on prostate-specific antigen (P SA) variability and usefulness in prostate cancer detection were exami ned. Methods. Percent change and crossover of PSA revels between the l ow (1.0 to 3.9 ng/mL) and high (4.0 to 10.0 ng/mL) ranges were evaluat ed in 72 men with benign prostatic hyperplasia (BPH) and 77 men with b oth BPH and prostate cancer (PCa) treated with finasteride or placebo for 6 months. Patients with PCa were studied as a model for evaluating the effects on PSA levels in patients with BPH and latent PCa. As rec ommended on the product label, PSA levels for finasteride-treated pati ents were doubled for interpretation. Results. In patients with BPH, m ost placebo- and finasteride-treated patients with low PSA levels at b aseline had subsequent PSA levels below 4.0 ng/mL throughout the study . Among patients with high baseline PSA levels, only 1 of 17 finasteri de-treated patients compared with 8 of 13 placebo-treated patients cro ssed into the low range. In the BPH/PCa study, most placebo-treated pa tients maintained PSA levels in the same range (15 of 19 less than 4.0 ng/mL; 14 of 16 greater than 4.0 ng/mL). Almost one third of finaster ide-treated patients with low PSA levels at baseline crossed into the high range (8 of 22), whereas most patients with high PSA levels at ba seline were not masked with treatment, with PSA revels remaining high (12 of 15). Conclusions. PSA levels cross between the low and high PSA ranges in both finasteride- and placebo-treated patients with BPH and those with both BPH and PCa. Doubling the PSA levels in finasteride-t reated patients allows appropriate interpretation of PSA values and do es not mask the detection of PCa. (C) 1997, Elsevier Science Inc. All rights reserved.