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Researchers are offering new hope of preventing cases of prostate cancer. The method: a generic pill that costs 40 cents a day. A newly released update of a large 10-year-old study shows this drug is more effective at preventing prostate cancer than was first thought. The study also addresses safety concerns, and it could increase the usefulness of the controversial PSA blood test to detect prostate cancer.
In a moment, we'll talk with a physician about the practical implications of the study. That's after this report from NPR's Richard Knox.
RICHARD KNOX, BYLINE: Eighteen thousand men signed up for the federally sponsored Prostate Cancer Prevention Trial. It was set up to see if a drug called finasteride could prevent prostate cancer by blocking a type of testosterone. The results were so good that the study was halted prematurely 10 years ago. Men who took finasteride had 25 percent fewer prostate cancers.
But Dr. Ian Thompson, who led the study, says there was a big hitch. Men who got prostate cancer despite taking the drug were more likely to get a more high-grade or lethal kind.
DR. IAN THOMPSON: It was immediately apparent that the main reduction was in the lower-grade cancers, and there was a slight increase of the higher-grade cancers.
KNOX: Doctors debated for years whether finasteride caused high-grade cancers or somehow just made them more likely to be detected. Recently, Thompson and his colleagues decided to go back and look at what happened to the men in the study. The results appear in this week's New England Journal of Medicine.
It turns out that finasteride is even more effective in preventing prostate cancer than they thought. Men who took the pill had 30 percent fewer prostate cancers instead of 25 percent.
THOMPSON: A 30 percent reduction is 50 to 80,000 fewer cancers per year. if everyone took it.
KNOX: That's great, but it doesn't translate into fewer prostate cancer deaths. After 18 years, men who took finasteride and those who took a placebo had exactly the same survival rate. That's because the prostate cancers prevented by finasteride are low-grade ones that aren't likely to kill.
THOMPSON: I think it's pretty clear that it doesn't make you live longer.
KNOX: But preventing low-grade, nonlethal prostate cancers is still a big deal.
THOMPSON: It significantly reduces the risk of a cancer diagnosis that can have profound negative consequences.
KNOX: The vast majority of men who get a diagnosis of prostate cancer of any kind get treated for it even if it wasn't destined to kill them.
THOMPSON: Many of the men have surgery. Many of the men have radiation. And those treatments have urinary and sexual side effects that are actually far more common than people think. So eliminating all of those cases would be a profound public health benefit.
KNOX: But what about the danger that finasteride might cause more killer cancers? The new study has good news on that front too. Although there were somewhat more high-grade cancers among the men who took finasteride, their death rate was exactly the same as men who took the placebo. Doctors aren't sure why.
THOMPSON: Even if there is a higher risk of high-grade cancer, it doesn't appear to have an impact on how long a man lives. And that's reassuring.
KNOX: Thompson says the results revive the idea of finasteride as a prostate cancer prevention pill. Dr. Dipen Parekh, chief of urology at the University of Miami, agrees. He says many doctors abandoned that idea after the Food and Drug Administration put a warning on finasteride in 2011.
DR. DIPEN PAREKH: That was a major, major deterrent to use these medications for prostate cancer prevention. Now, with the most recent results, I think this should reopen the doors for a lot of us who believe that, you know, we can judiciously use preventative agents for prostate cancer.
KNOX: And he thinks the findings could rejuvenate enthusiasm for the use of the PSA test to screen men for prostate cancer. The big rap on PSA is that it reveals many low-grade cancers that really don't need to be treated. But finasteride prevents many of those. And because it shrinks the prostate, the drug increases doctors' ability to find cancers worth worrying about.
PAREKH: That has a potential to revolutionize the way we think about prostate cancer.
KNOX: The drug causes sexual side effects in some men, but it also reduces urinary problems suffered by many men in middle age and beyond. Richard Knox, NPR News.
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