NEW YORK (Reuters Health) Jul 15 - Low-dose aspirin, even if not taken daily, may reduce a woman's risk of colon cancer over the long term, according to new data from the Women's Health Study.
The apparent benefit came at a cost, as women taking aspirin also had higher rates of gastric bleeding and ulcers.
But women who took 100 mg of aspirin every other day for at least 10 years ended up with about a 20% lower risk of colon cancer after some 18 years of follow-up, compared to women who took a placebo.
"We were quite surprised to see it actually," said lead author Dr. Nancy Cook from Boston's Brigham and Women's Hospital, because some researchers had believed that 100 mg of aspirin every other day was too little and too infrequent to matter.
The new study, published online July 15th in Annals of Internal Medicine, is a follow-up to an earlier report that found no difference in colon cancer risk among the women during the initial observation period, which lasted a median 10 years.
In the trial, about 40,000 women age 45 and older were randomly assigned to take low-dose aspirin or a placebo every other day starting between 1993 and 1996. They were followed through 2004.
For the new report, about 34,000 of the women from that original group agreed to continue taking yearly surveys through March 2012. They no longer received aspirin or placebo pills, though some continued taking aspirin on their own.
The researchers say that over 16 years, the women who took low-dose aspirin every other day during the original study period had a colorectal cancer incidence of 11 cases per 1,000 people, compared to 14 cases per 1,000 people who took a placebo.
The risk reduction was greatest in women who continued to take aspirin after the original trial, according to the researchers.
There was no effect, however, on risk for cancers of the breast or lung.
"The new results from the Women's Health Study provide important evidence confirming that low-dose aspirin use does indeed lower risk of colorectal cancer, but that this benefit does not 'kick in' until about 10 years after the start of regular use," Dr. Eric Jacobs, strategic director of pharmacoepidemiology at the American Cancer Society in Atlanta, wrote in an email to Reuters Health.
Dr. Jacobs, who has researched aspirin use and the risk of cancer but wasn't involved in the new study, cautioned that there are known side effects of taking aspirin.
"It is important to remember that aspirin is a real drug with real side effects, including sometimes causing serious, even occasionally fatal, stomach bleeding, even at low doses," he wrote.
"Aspirin use is recommended for most people who have had a heart attack, and has some benefits for colorectal cancer as well, but at this point the American Cancer Society does not recommend that people use aspirin specifically to prevent cancer," Dr. Jacobs noted.
Dr. Cook and her colleagues found that women who took aspirin were 14% more likely to have stomach bleeding and 17% more likely to develop peptic ulcers.
Still, she said, "the benefits may outweigh those (risks) because you would be preventing more heart attacks and strokes," adding that the decision to take aspirin should be based on an individual's specific risks.
SOURCE: http://bit.ly/12F0jOK
Ann Intern Med 2013.
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