After 18 years of follow-up, the drug finasteride was shown to reduce the risk for prostate cancer by approximately one third, but did not significantly affect overall survival in men or survival after prostate cancer diagnosis.

Finasteride is one of the 5-alpha reductase inhibitors, none of which is approved for use in the prevention of prostate cancer. The agent is used in the treatment of male- pattern baldness and benign prostatic hypertrophy.

In the Prostate Cancer Prevention Trial (PCPT), which began in 1993, finasteride was shown to reduce prostate risk, but was also linked with an increased risk for high-grade disease compared with placebo.

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With up to 18 years of follow-up data from the PCPT to analyze, Ian M. Thompson, Jr, MD, director of the Cancer Therapy & Research Center at The University of Texas Health Science Center in San Antonio, Texas, and colleagues evaluated survival rates among all study participants and among those with prostate cancer. The investigators reported their findings in The New England Journal of Medicine (2013;369:603-610).

Among 18,880 PCPT participants randomized to finasteride or placebo, 10.5% (989 of 9,423) in the finasteride group and 14.9% (1,412 of 9,457) in the placebo group received a diagnosis of prostate cancer during the follow-up period. Of the men who were evaluated, 333 (3.5%) in the finasteride group had high-grade cancer (Gleason score 7 to 10), compared with 286 (3.0%) in the placebo group.

Finasteride had no significant impact on either overall survival or survival after prostate cancer diagnosis. Among the men who died, 15-year survival rates were nearly identical between groups: 78.0% for the finasteride users (2,538 deaths) and 78.2% for the placebo users (2,496 deaths).

Thompson’s team also calculated 10-year survival rates: 83.0% in the finasteride group and 80.9% in the placebo group for men with low-grade prostate cancer, and 73.0% and 73.6%, respectively, for those with high-grade disease.