It's a drug used to treat an enlarged prostate, as well as male-pattern baldness, and 10 years ago a study indicated it could reduce a man's risk of developing prostate cancer by 30 percent.
But there was also some indication that the drug, generic name finasteride, might cause more aggressive prostate tumors, so the Food and Drug Administration added a black box warning about the potential risks and wouldn't approve its use to prevent cancer. Doctors also backed away from prescribing it.
Now new research confirms the drug's potential benefits, and at least one prostate cancer expert tells AARP that the FDA should reconsider and remove the warning.
The follow-up study - which looked at nearly 19,000 men, average age 62, who took the drug for seven years - confirms that finasteride reduces the risk of prostate cancer by about a third, and the risk of low-grade tumors by 43 percent.
What that means, explained lead author Ian M. Thompson Jr., M.D., of the University of Texas Health Science Center at San Antonio, is that taking the drug could prevent 71,000 men each year from getting treated for low-grade prostate cancer.
"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," he added.
There were slightly more high-grade tumors in the group that took the drug compared with those in a placebo group - 3.5 percent versus 3 percent - but that may be because finasteride shrinks the prostate, so doctors can detect serious tumors more easily during a biopsy.
"This drug wasn't causing more prostate cancer. It's causing more prostate cancer to be diagnosed" because it's easier to find, Otis Brawley, M.D., chief medical officer for the American Cancer Society told WebMD.
In any case, after 18 years of follow-up, researchers found no significant difference in the death rate between the drug group and the placebo group, the study noted.
"I hope the FDA will consider this data and take back the black box warning," so doctors and patients are reassured that the drug is safe to take, says Eric Klein, M.D., chairman of the Glickman Urological and Kidney Institute at the Cleveland Clinic.
Klein, who enrolled some of his patients in the study but was otherwise not involved, says the results don't mean every man should take finasteride to prevent prostate cancer.
"If you're having urinary symptoms due to an enlarged prostate, if there's a family history of prostate cancer, if you've had a negative biopsy because of a worrisome PSA test score, then it makes perfect sense," he says.
The drug can cause some side effects, including erectile dysfunction.
Perhaps the drug's biggest contribution, Klein adds, is to keep men from being unnecessarily treated for low-grade tumors.
"In common urologic practice today, most men get treated for low-grade cancer," even though it may never become dangerous, because patients get nervous about watchful waiting, and urologists have professional and sometimes financial incentives for referring patients for radiation, he said.
But if taking finasteride can reduce the chance of those low-grade tumors from occurring, it could prevent men from getting unneeded treatment that can have unpleasant and lasting side effects, including impotence and incontinence.
The study was published Aug. 15 in the New England Journal of Medicine and was funded by the National Cancer Institute.
Photo: Credit: Caro/Alamy
Also of Interest
- Overcoming Loss of Libido After Cancer
- Juicer vs. Blender: Which Is Healthier For You?
- Join AARP: Savings, resources and news for your well-being
See the AARP home page for deals, savings tips, trivia and more