Low doses of aspirin taken to reduce the risk of heart attacks and strokes can also lower the risk of colon cancer, British researchers reported.
They found that aspirin reduced the number of cases of colorectal cancer by a quarter and cut colon cancer deaths by a third.
They said their findings may tip the balance in favor of using aspirin to prevent colon cancer, which is the second most common form of cancer in developed countries after lung cancer.
But their findings, published in the Lancet medical journal, are unlikely to settle a matter that doctors consider controversial.
Many studies have shown that people who take high doses of aspirin are less likely to develop colon cancer and the little growths called polyps that can develop into cancer.
But aspirin itself can be dangerous to many people, causing sometimes deadly bleeding in the stomach and intestines.
Other studies have found that a related painkiller, ibuprofen, can also reduce colon cancer rates among people who take it regularly over the long term.
Peter Rothwell of John Radcliffe Hospital in Oxford and colleagues looked at four big studies of 14,000 people, half of them taking low-dose aspirin for heart disease. These lower doses of aspirin are considered much safer.
Over about 18 years, they reported, 2.8 percent of the volunteers developed colon cancer.
Aspirin reduced the 20-year risk of colon cancer by 24 percent and lowered the risk that a patient would die from colon cancer by 35 percent, they said.
"This interesting study would incite clinicians to turn to primary prevention of colorectal cancer by aspirin at least in high risk-populations. Specific guidelines for aspirin chemoprevention would be the next logical step," Dr. Robert Benamouzig and Dr. Bernard Uzzan of Avicenne Hospital in Bobigny, France, wrote in a commentary.
In many developed countries like the United States and Britain, doctors recommend getting regular cancer checks using instruments that can examine the colon from the inside.
Britain's National Health Service often opts for a procedure called a sigmoidoscopy, while U.S. experts call for a more comprehensive screening called a colonoscopy.
Both procedures can detect the pre-cancerous growths called polyps so doctors can remove them before they form a tumor, but patients are reluctant to get these uncomfortable and embarrassing tests. Some experts are hoping using cheap drugs like aspirin may be a way to prevent colon cancer in the population