Finasteride Comes Out on Top in Prostate Cancer Trial

Five years ago, interim results from the large-scale Prostate Cancer Prevention Trial showed that finasteride reduced relative risk of the disease by about 25 percent—from 24.4 percent down to 18.4 percent. The news excited researchers, but the study also showed that men who did develop prostate cancer while taking the drug had a higher risk of high-grade, or aggressive, cancer.

Scientists theorized that the drug could be jump-starting aggressive cancers, or that the observed decrease in risk could be attributed to cancers that never would have progressed.

Now, three new analyses of the PCPT data indicate researchers may have underestimated finasteride’s benefit. Scientists have determined that finasteride lowers the relative risk of aggressive prostate cancer by 27 percent (8.2 percent of men were diagnosed with high-grade cancers compared with 6 percent of patients taking finasteride). And after re-examining biopsy samples from patients in the placebo arm, researchers found that three-quarters of those cancers would have progressed—quelling the argument that finasteride merely reduced the risk of cancers that would never have become life-threatening.

Finasteride could also improve the accuracy of prostate biopsies by shrinking the gland and increasing the chance tumors could be found. And a previous study published in the Journal of the National Cancer Institute showed that PSA (prostate-specific antigen) tests were also more accurate in men taking the drug because finasteride lowered PSA levels resulting from non-cancer causes, such as benign prostatic hyperplasia (BPH). Plus, the drug seems to have very few side effects.

Men at high risk, such as those with a family history of prostate cancer, are good candidates for the chemopreventive drug, say experts. A second-generation drug, Avodart (dutasteride), which is currently approved to shrink enlarging prostates, is in phase III clinical testing for prostate cancer prevention and may ultimately be even better than finasteride.