New Data May Dispel Safety Concerns With 5-ARI Use in Prostate Cancer Prevention

Ian M. Thompson, Jr, MD

The Prostate Cancer Prevention Trial (PCPT), conducted from January 1997 to February 2003, demonstrated that the 5α-reductase inhibitor (5-ARI) finasteride reduced the risk of developing prostate cancer in men being regularly screened for the disease; however, at the time, researchers observed that men receiving the drug were more likely to develop high-grade prostate cancer.

Now, 18 years after the first PCPT patient was randomized, a long-term follow-up has confirmed the preventive benefit of finasteride use. Specifically, the drug proved to be highly effective in reducing the low-grade cancers associated with the overdetection and overtreatment of the disease. Further, the follow-up study dispelled the safety concerns raised in the initial research. The follow-up results were published in The New England Journal of Medicine.

When the results of the PCPT trial were first published in 2003, that data showed that finasteride reduced the relative risk of prostate cancer by 24.8%. However, the researchers also observed a relative increase of 26.9% in the rate of high-grade prostate cancers in patients who received finasteride compared with those who received a placebo. Ian M. Thompson, Jr, MD, professor in the Department of Urology and director of the University of Texas Cancer Therapy and Research Center, and his colleagues wanted to determine whether this increased risk of developing high-grade prostate cancer had any effect on longterm survival. Thompson et al’s current research provides updated survival data through October 31, 2011.

The researchers found that among the 18,880 eligible men who were randomized in the study, 989 of 9423 patients in the finasteride group (10.5%) were diagnosed with prostate cancer, compared with 1412 of 9457 patients in the placebo group (14.9%; relative risk in the finasteride group = 0.70; 95% CI, 0.65-0.76; P <.001). Among the patients who were evaluated in the study, 333 patients in the finasteride group (3.5%) developed high-grade cancer, defined as a Gleason score of 7 to 10, compared with 286 patients in the placebo group (3.0%; relative risk = 1.17; 95% CI, 1.00-1.37; P = .05).

Using the Social Security Death Index, the researchers determined that 2538 patients in the finasteride group and 2496 patients in the placebo group had died by October 31, 2011. This translated into 15-year survival rates of 78.0% and 78.2%, respectively. The unadjusted hazard ratio for death in patients who received finasteride was 1.02 (95% CI, 0.97-1.08; P = .46).

Additionally, the 10-year survival rates were 83.0% in the finasteride arm of the study compared with 80.9% in the placebo arm for patients who were diagnosed with low-grade prostate cancer. In the high-grade prostate cancer group, the survival rates were 73.0% and 73.6%, respectively.

“If you look at the number of prostate cancers that are diagnosed annually and multiply that by 30%, that’s the number of cancers we might be able to prevent each year,” Thompson said. “That’s more than 71,000 men. That’s more than 175 jumbo jets full of men who won’t get cancer, who won’t face treatments with side effects like sexual dysfunction. There’s nothing like disease prevention. Nothing comes close.”

Thompson, IM, Goodman PJ, Tangen CM, et al. Long-term survival of participants in the Prostate Cancer Prevention Trial. N Engl J Med. 2013;369(7):603-610.