Oct. 22, 2010 - Long-term use of low-dose aspirin reduces colon cancer risk, U.K. researchers find.

Low-dose aspirin takers have a 24% lower risk of colon cancer and a 35% lower risk of dying from colon cancer, find University of Oxford researcher Peter Rothwell and colleagues.

"The new findings on the effect of low-dose aspirin should be included in advice given to the public," Rothwell says in a news release.

The findings are based on analysis of 20-year follow-up data from five clinical trials. All of the studies were performed before sigmoidoscopy and colonoscopy became widespread methods of screening for colon cancer. It's not clear whether better screening reduces the benefit seen for aspirin.

And aspirin can have serious side effects, including severe stomach bleeding. While low doses of aspirin reduce this risk, people should consult a health care provider before adding aspirin to their daily health regimen.

However, the findings suggest that aspirin has a particular effect on more aggressive and faster growing colon cancers, particularly those in the proximal colon, which can be detected by colonoscopy but not by sigmoidoscopy.

This makes the study findings significant, says Alison Ross, senior science information officer at Cancer Research U.K.

"This is the first large study to show that low doses of aspirin may be effective in protecting against bowel cancer," Ross tells WebMD via email. "Once it’s confirmed that the benefits of taking low-dose aspirin outweigh the risks, clear guidelines will be needed to help doctors inform their patients about long-term use."

Alison Ross, senior science information officer at Cancer Research UK, says via email: "Aspirin can have side effects, including stomach ulcers and internal bleeding. It should not be taken regularly without first talking to your doctor."

The Rothwell study appears in the Oct. 22 early online edition of The Lancet.