On Jun. 24, 2003, results of the Prostate Cancer Prevention Trial (PCPT), testing the effectiveness of finasteride to prevent the disease, were announced about a year earlier than expected.

The PCPT was the first study to show that a drug can reduce a man’s chances of developing prostate cancer. The initial evaluation showed that men randomized to take finasteride were 25 percent less likely to develop prostate cancers than men in the placebo group. This evaluation focused on the men who had their end-of-study biopsy or who had been diagnosed with prostate cancer during the study.

There was a note of caution, however; the men who did develop prostate cancer while taking finasteride were more likely to have high-grade tumors.