Data show drug’s benefit in preventing prostate cancer

In 2003, the Prostate Cancer Prevention Trial found that men taking the drug finasteride could reduce their overall risk of developing prostate cancer by 25%. But the study also indicated that the drug increased the risk of developing aggressive prostate cancer in some men. Given the contradictory findings, few doctors recommended finasteride for prostate cancer prevention.

A new analysis of the data and assessment of prostate tissue biopsies collected as part of the trial has potentially resolved these concerns. In addition to reducing overall prostate cancer risk by 25% to 30%, finasteride showed no tendency to increase the rate of aggressive tumors. In fact, it likely decreased the rate of aggressive tumors by 27%.

The drug’s ability to shrink the prostate might be the cause of the discrepancy between the two studies, researchers said. Because the prostates were smaller in men who took finasteride, the cancer appeared to take up more prostate tissue, making it easier to find in the initial biopsies. And in the first study, cancer was probably missed more often on biopsies of men who took a placebo because the prostate gland itself was larger.

Finasteride is typically prescribed to shrink the prostate in men with benign prostatic hyperplasia (BPH). An enlarged prostate can constrict the urethra, which carries urine out of the body.

“A man who is undergoing prostate cancer screening should be informed that he may reduce his risk of prostate cancer by about 25%,” said Dr. Ian Thompson, Jr., who announced the most recent findings at the American Urological Association’s annual meeting in May 2008. “That strategy, in a country where about 200,000 men are diagnosed with prostate cancer each year, would have substantial public health benefits.”

Whether these new findings will alter prescribing patterns remains to be seen.

SOURCES: Thompson IM, Goodman PJ, Tangen CM, et al. The Influence of Finasteride on the Development of Prostate Cancer. The New England Journal of Medicine 2003;349:215–24. PMID: 12824459.

Redman MW, Tangen CM, Goodman, PJ, et al. Finasteride Does Not Increase the Risk of High-Grade Prostate Cancer: A Bias-Adjusted Modeling Approach. Cancer Prevention Research 2008; Online First 2008:OF1–8.

Originally published April 2009; last reviewed February 24,2011.

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