Prostate cancer prevention and finasteride.

We assessed whether the association between the larger changes in prostate specific antigen and high grade prostate cancer observed in the Prostate Cancer Prevention Trial can explain the increased detection of high grade prostate cancer in men randomized to finasteride vs placebo. A literature review was performed to obtain evidence to develop a hypothesis that may explain the results of the Prostate Cancer Prevention Trial. On average finasteride halved prostate specific antigen. As shown by the Medical Therapy of Prostatic Symptoms study and Prostate Cancer Prevention Trial, it also decreased the annual median increase in prostate specific antigen from benign prostatic hyperplasia. Therefore, despite doubling prostate specific antigen during the first 3 years of the Prostate Cancer Prevention Trial, to have prostate specific antigen exceed 4 ng/ml and have a prostate biopsy recommended men receiving finasteride vs placebo required greater increases in prostate specific antigen, which was shown in the Prostate Cancer Prevention Trial to be associated with high grade disease (p < 0.001). Also, the decrease of the contribution to prostate specific antigen from benign prostatic hyperplasia by finasteride improved the performance characteristics of prostate specific antigen to detect Gleason score 7 or higher prostate cancer. By decreasing the contribution to prostate specific antigen from benign prostatic hyperplasia finasteride makes changes in prostate specific antigen more cancer specific. This effect may explain the increased detection of high grade prostate cancer in men randomized to finasteride in the Prostate Cancer Prevention Trial. How to best use prostate specific antigen to recommend biopsy in men on 5alpha-reductase inhibitors requires further study.