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Little pill's big conundrums

By ASSOCIATED PRESS
Published April 24, 2007

WASHINGTON - The research could give you whiplash: Aspirin prevents cancer, one study says. Oops, maybe not, says another.

Now comes word that aspirin may fend off cancer only if people take much more than is used to fight heart disease, suggesting some of the earlier back-and-forth may have been confusion over the right dose.

Even that evidence is circumstantial, offering no end to the competing headlines.

"A general perspective that people have is, 'Why is it so difficult to get a clear answer on a pill that costs a few pennies and is available over-the-counter and taken by millions of people?' " says the American Cancer Society's Dr. Michael Thun, a co-author of the newest study.

For decades, scientists have chased the hope that aspirin could be an easy way to prevent certain cancers. The idea: Aspirin fights inflammation, and thus pain, by inhibiting substances known as cyclooxygenase, or COX, enzymes. COX enzymes also are involved in the formation of certain kinds of tumors, such as colorectal, prostate and breast cancers.

Aspirin does something else, as well: It makes blood less likely to form clots, giving it an important role in fighting heart disease. In contrast, connecting the cancer dots - showing that reducing COX would in turn reduce tumors - is vexing.

Fast Facts:

Cancer research

Some recent research on aspirin and cancer:

- Taking an adult-strength aspirin daily for at least five years was associated with a 30 percent lower risk of colorectal cancer, a 20 percent lower risk of prostate cancer and a 15 percent lower risk of cancer overall, American Cancer Society researchers reported last week.

- Last month, a report from the long-running Nurses Health Study found women who took low to moderate aspirin doses had a 12 percent lower risk of death from cancer.

- But in 2005, another report from the nurses study suggested aspirin helped prevent colorectal cancer only if women took low doses for a decade.

- Also in 2005, the more rigorous Women's Health Study found women assigned to take a baby aspirin every other day for 10 years were no less likely to have cancers than women on dummy pills.

[Last modified April 24, 2007, 01:10:27]