It May Block Colorectal Cancer
Aspirin's latest feat
The aspirin tablet is a wonder drug that eases pain, brings down fevers, prevents heart attacks and stroke and will even keep your flowers fresh if you dissolve a tablet in water. Now, says a paper published in the New England Journal of Medicine, it appears this little pill can ward off colorectal cancer, too.
To those who have been following the arcana of epidemiological literature, the results of this latest study may not come as news. All but one of 16 previous studies over the past decade have found that aspirin reduces the risk of colorectal cancer, which will strike about 138,000 Americans this year and kill 55,000. But that one dissenting study provoked serious doubt about aspirin's effect on colorectal cancer because it was a randomized placebo-controlled trial. In the study, half of 22,000 physicians were given an aspirin every other day while the other half took a placebo. When the trial was halted after six years, it was clear that the doctors taking aspirin suffered a dramatically lower incidence of heart attacks and stroke, but there was no evidence that the drug had protected them from colorectal cancer.
Lag time. The reason, as this latest study finally demonstrates, is that aspirin's ability to keep colorectal cancer at bay doesn't show up for at least a decade. Edward Giovannucci and his team of epidemiologists at the Harvard School of Public Health looked at the records of 89,446 nurses who have participated in the Nurse's Health Study since 1976. The researchers found that nurses who took at least four to six aspirin pills per week for 10 years--for reasons ranging from sore muscles to headaches to reducing their risk of heart attack--were slightly less likely to be hit with colorectal cancer than were those nurses who didn't take aspirin. After two decades, however, aspirin's power to protect them went up dramatically, cutting their risk by nearly half. The drug takes so long to kick in, says Giovannucci, because it takes that long for colorectal cancer to develop, and aspirin may only be able to keep tumors at bay when they are in their earliest stages.
Unfortunately, there's no evidence it has an effect on any malignancy other than colorectal cancer, and nobody knows why. In fact, says Aaron Marcus, of the New York Veterans Affairs Medical Center and Cornell University Medical College, "nobody has any idea how aspirin really works." It seems to prevent heart attacks by keeping blood cells, known as platelets, from sticking together and blocking arteries already clogged by too many french fries and cheeseburgers. Still, researchers do not understand how aspirin interferes with the course of colon cancer.
That's not stopping Marcus from recommending that anybody over the age of 50 with a history of colorectal or breast cancer in the family consider taking an aspirin every other day. The American Cancer Society isn't ready to make quite so bold a statement until several ongoing studies have been completed, because aspirin poses serious risks, including interfering with the blood's capacity for clotting. In the meantime, the society is considering convening a panel to provide guidelines to doctors. While they're at it, maybe they can figure out a way to make those #@$!&* childproof aspirin bottles easier to open.
WHEN TO TAKE OR AVOID ASPIRIN Be sure to consult your doctor about whether to take an aspirin every other day. Things to ponder:
DO'S Consider taking it if you:
are over 50
have had colorectal cancer or have had polyps removed
have a family history of colorectal or breast cancer
are at risk for heart attack
DON'TS ... but aspirin can trigger:
asthma attacks
Reye's syndrome, a sometimes fatal disorder
bleeding in the stomach and intestine
hemorrhagic stroke
reduced sperm motility
This story appears in the September 18, 1995 print edition of U.S. News & World Report.
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