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Aspirin May Lower Women's Colon Cancer Risk

Benefit must be weighed against GI bleeding, other risks, however, experts say

WebMD News from HealthDay

By Kathleen Doheny

HealthDay Reporter

MONDAY, July 15 (HealthDay News) -- Taking a low-dose aspirin every other day may reduce the risk of colorectal cancer, according to a study that focused on nearly 40,000 women aged 45 and older.

The protection does seem to take some time to surface, said researcher Nancy Cook, a professor of medicine at Brigham and Women's Hospital and Harvard Medical School. "After 10 years, we started to see an effect," she noted.

"After 18 years of follow-up, we saw a 20 percent reduction in colon cancer over the whole time period," she said. When they looked at the 10-to-18 year mark, the reduction was 42 percent, she said.

However, risks linked with aspirin, such as gastrointestinal bleeding, must be considered, Cook said.

The study, funded by the U.S. National Cancer Institute and U.S. National Heart, Lung, and Blood Institute, is published July 16 in the Annals of Internal Medicine.

Aspirin has been long known for its protective effects on heart health, but the protective effect of aspirin on colon and rectal cancer has only been found more recently. "In the past three years, analyses of trials conducted for cardiovascular health have begun to show an effect on colon cancer as well," Cook said.

Cook and her team followed women enrolled in the Women's Health Study, a trial that evaluated the benefits and risks of low-dose aspirin and vitamin E in preventing both cardiovascular disease and cancers.

The study began in 1993 and ended in 2004. The women had no history of cancer (except nonmelanoma skin cancer), cardiovascular disease or other major chronic illness when they enrolled.

The women assigned to the aspirin group were told to take a low dose -- 100 milligrams -- of aspirin every other day. The comparison group took placebo pills on alternate days.

After the study ended, the researchers continued to follow more than 33,000 women through March 2012. The women were told to continue the regimen, although the researchers no longer provided the pills.

The researchers tracked colorectal cancer, along with other cancers. They found the 20 percent lower colorectal cancer incidence over the entire 18-year follow-up.

They did not find a difference with cancer deaths between groups, but Cook said there may not have been enough women to show a comparative difference from a statistical point of view.

Cook found no difference in colorectal polyps between groups. Polyps are removed when they are found on colonoscopy as they can progress to cancer.

The aspirin group had more gastrointestinal bleeding, a known side effect, and more peptic ulcers. While 8.3 percent of the aspirin group had GI bleeding, 7.3 percent of the placebo group did. Peptic ulcers affected 7.3 percent of the aspirin group but only 6.2 percent of the placebo group.

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