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A study in this week's Journal of the American Medical Association shows that regular use of aspirin and painkillers such as ibuprofen is highly effective at preventing colon cancer in women. Even so, experts say people shouldn't take painkillers to prevent cancer. NPR's Richard Knox explains why.
RICHARD KNOX reporting:
First, let's review what doctors already knew about aspirin and disease prevention. They knew that a baby aspirin a day can prevent heart attacks and death in people with heart disease and in healthy men and healthy older women without known heart disease. But when it comes to cancer, the picture's been murky. Some studies show aspirin can prevent recurrence of colon polyps, which often give rise to cancer. It should follow that regular aspirin users have lower risk of colon cancer. But solid proof has been hard to find.
Now comes a new analysis of 83,000 nurses. Harvard researchers have monitored their use of aspirin and other painkillers for 20 years. Dr. Andrew Chan of Massachusetts General Hospital led the study.
Dr. ANDREW CHAN (Massachusetts General Hospital): We did find that regular long-term aspirin use reduces the risk of colorectal cancer. And we found a similar benefit for NSAIDs, or non-steroidal inflammatory drugs, which we believe has a similar anti-cancer mechanism to aspirin.
KNOX: Chan says the reduction in cancer risk is substantial.
Dr. CHAN: We found overall in individuals that took more than 14 tablets per week about 30 to 40 percent risk reduction. If people took it for more than 10 years consistently at that higher dose, we found an even greater risk reduction.
KNOX: More than 50 percent fewer colon cancers. But pay attention to the fine print. There was no benefit from taking painkillers for less than a decade, and the biggest payoff was restricted to women taking big doses--with aspirin, for example, two regular, not baby, aspirin every day. For women who took less, say two to five tablets a week, the cancer prevention benefit was much less. And women who took a lot of painkillers were much more likely to have intestinal bleeding. Chan puts that into perspective.
Dr. CHAN: If we treated roughly 10,000 women over about a one-year period with a high-dose aspirin regiment, we would expect to prevent about one or two cases of colorectal cancer. But that would be at the expense of potentially eight cases of major bleeding.
KNOX: Now some people might fear colon cancer more than they fear gastrointestinal, or GI, bleeding. But Dr. Michael Thun of the American Cancer Society warns against this kind of thinking.
Dr. MICHAEL THUN (American Cancer Society): Well, a GI bleed seems more minor if it's not you who has it. If you're having a formal recommendation for a preventive treatment and you're causing things that require hospitalizations or transfusions in people who are otherwise healthy, then it's a side effect that's serious.
KNOX: Until recently, researchers hoped that so-called COX-2 inhibitors such as Celebrex might prevent colon cancer without the bleeding risk. But now that the COX-2s have been implicated in heart disease, Thun says that doesn't seem like a good tradeoff. But he thinks one day aspirin may be a good cancer preventer for some people.
Dr. THUN: The hope is that as we keep studying this, we'll be able to identify people who are at sufficiently high risk of colon cancer or who may be protected against other cancers by aspirin, in which we can put together the heart disease and the cancer recommendations. But we're a long way from that.
KNOX: Meanwhile, people should put away their bottles of regular-size painkillers unless they have pain. Richard Knox, NPR News, Boston.
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