T aking low-dose aspirin-often recom- mended to protect your heart-may also reduce your odds of colon cancer. A team of researchers whod previously shown a link between high-dose aspirin and lower colon-cancer risk looked at fve trials totaling 16,488 participants taking lower doses, since long-term high-dose aspirin usage can have adverse bleeding effects. Over nearly 20 years of followup, the new analysis found that people assigned to low- dose aspirin regimens for six years were at one-quarter lower risk of colon cancer and one-third less likely to die of the disease.
Longer periods of low-dose aspirin use were associated with an even greater 70% reduced risk of colon cancer and also with lower rates of rectal cancer. The amounts of aspirin assigned in the trials varied widely, but the analysis showed that a 75-milligram daily dose was as effective in preventing colon cancer as larger doses.
T he reduction in colon cancer was limited to the proximal colon-the portion farthest from the rectum-and the results seemed to suggest a difference in tumor aggressiveness in patients on an aspirin regimen. This led researchers Peter M. Rothwell, MD, PhD, of the University of Oxford, and colleagues to comment, The suggestion of a particular effect of aspirin on more aggressive and rapidly growing tumors might allow less frequent screening. They added that the prevention of proximal colonic cancers by aspirin, which would not be identifed by sigmoidoscopy screening and for which colonoscopy screening is only partly effective, is clearly important.
Patients in the trials, researchers cau- tioned, were mostly men at high cardiovas- cular risk, so its not clear that the fndings can be extended to the population at large.
In an accompanying commentary in The Lancet, Robert Benamouzig, MD, and Bernard Uzzan, MD, of Avicenne Hospital in France, also cautioned that the trials were not primarily designed to study colon can- cer. But they wrote that the fndings might encourage clinicians to attempt primary prevention of colorectal cancer by aspirin, at least in high-risk populations.
Before beginning any aspirin regimen, consult your physician. The Lancet, online before print; abstract at<www.thelancet.com/journals/lancet/ article/PIIS0140-6736(10)61543-7/fulltext>