TUESDAY, Aug. 23, 2005 (HealthDay News) -- People who take aspirin or a non-steroidal anti-inflammatory drug (NSAID) such as Advil or Motrin to treat their arthritis or other pain may also be lowering their risk of colorectal cancer.
But the benefits of the drug therapy don't become significantly apparent for at least a decade, according to new research. And the therapy poses considerable health risks, including gastrointestinal bleeding as a result of such long-term use.
Harvard researchers report that long-term use of aspirin or NSAIDs cuts colorectal risk by as much as 53 percent. The risk reduction depended on the dose taken weekly and the number of years taken, according to the study, published in the Aug. 24-31 issue of the Journal of the American Medical Association.
"Regular long-term use of aspirin did reduce the risk of colorectal cancer," said the study's lead author, Dr. Andrew Chan, an instructor of medicine at Harvard Medical School and a staff physician at Massachusetts General Hospital in Boston.
However, Chan also urged caution, because long-term use of these medications can cause serious side effects, including gastrointestinal bleeding.
He said the researchers were not recommending either aspirin or NSAIDs for routine colorectal cancer prevention.
"You have to weigh both the risks of colorectal cancer and the side effects of using these drugs. There are other prevention strategies, like colorectal cancer screening, and we need to examine what the benefit of aspirin would be above and beyond current prevention," said Chan.
The American Cancer Society agreed. In a statement, Eric Jacobs, a senior epidemiologist for the society, said that "use of aspirin at any dose to prevent cancer is not recommended by the American Cancer Society or any other group because of the potential for serious side effects."
Although advances have been made in screening and detection of colorectal cancer, it still remains the second most deadly form of the disease, after lung cancer. Each year, about 56,000 Americans die from colorectal cancer and 145,000 people will be newly diagnosed with the illness, according to the American Cancer Society.
Using information from the prospective Nurses' Health Study, the researchers examined data on nearly 83,000 women who had been providing information on their medication use at least every two years. The women were between 30 and 55 at the start of the study.
In this group, 962 women developed colorectal cancer during the 20-year study period.
Women who regularly used aspirin were at a 23 percent reduced risk of colorectal cancer compared to non-regular aspirin users, according to the study. Significant risk reduction didn't appear until after a decade of use, however.
The researchers also found that the more aspirin the women took, the lower their colorectal cancer risk. Women who took two to five standard aspirin tablets weekly had an 11 percent reduced risk compared to non-users. The risk fell by 22 percent among women who took six to 14 tablets weekly, while women taking more than 14 aspirin tablets a week had a 32 percent decrease in their risk of colorectal cancer.
Women who took more than 14 tablets weekly for more than 10 years had the greatest risk reduction, 53 percent, according to the researchers.
However, Chan said that women on the highest doses of aspirin also increased their risk of gastrointestinal bleeding by 57 percent.
Dose also mattered for NSAIDs -- drugs that include Advil, Aleve and Motrin. Women taking two to five tablets a week lowered their colorectal cancer risk by 9 percent, while those taking six to 14 tablets weekly had a 31 percent decreased risk. Women taking more than 14 NSAID doses a week reduced their risk by 46 percent, according to the study.
NSAIDs were also associated with an increased risk of gastrointestinal bleeding, Chan said.
Chan said the researchers also looked at the effects of acetaminophen (Tylenol) and weren't surprised when they found no benefit. That's because the researchers suspect that inhibition of the enzyme cox 2 -- something both aspirin and NSAIDs do -- may be what's reducing colorectal cancer risk. Acetaminophen does not inhibit cox 2.
Two prescription cox 2 inhibitor NSAIDS -- Vioxx and Bextra -- have been pulled from the market because long-term use has been linked to serious cardiovascular side effects, but one such drug, Celebrex, remains on drugstore shelves. Chan said his team's study was unable to determine whether long-term use of over-the-counter NSAIDs might have similar effects.
While the researchers aren't recommending the routine use of aspirin or NSAIDs for colorectal cancer prevention, Chan said there may be a use for these drugs in some patients, perhaps those at an especially high risk for the malignancy. But, he said, it's too soon to know for sure.
What this study does do, he said, is "validate our understanding of the mechanism behind colorectal cancer and opens further avenues of research."
Both Chan and Jacobs said the best way to prevent colorectal cancer is to undergo regular colorectal cancer screenings beginning at age 50, or even sooner for individuals at high risk for the disease.
More information
To learn more about colorectal cancer, visit the U.S. Centers for Disease Control and Prevention.
