Daily Aspirin Cuts Colon Cancer Risk in People Genetically Prone to the Disease

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Colon cancer is one of the most common cancers in the United States, diagnosed in more than 130,000 new patients each year. For most people, the life-time risk for developing colon cancer is about six percent, but the risk is more pronounced for those with hereditary colon cancer syndromes. Patients who have inherited one of these syndromes have an extremely high risk for developing colon cancer, approaching 90 to 100 percent. However, European researchers say people with the most common of these syndromes, Lynch syndrome, could significantly reduce their chances of developing colon cancer by taking daily doses of an inexpensive over-the-counter drug that’s been around for better than a century and continues to be at the forefront of emerging science—aspirin.

The researchers came to this conclusion after following 1,071 people with Lynch syndrome, which accounts for about five percent of all colon cancer. For about four years, half of the participants were given daily doses of 600 milligrams of aspirin, while the other half received a placebo. Tests done 29 months into the study showed no difference in colon cancer rates, but a follow-up after four years detected a significant difference. “To date, there have been only six colon cancers in the aspirin group as opposed to 16 who took placebo,” said John Burn of the Institute of Human Genetics at Newcastle University in Britain, who led the study. “There is also a reduction in endometrial cancer.”

A previous study by Harvard Medical School researchers found that regular use of aspirin may reduce the mortality risk of colon cancer by more than half by inhibiting the enzyme COX-2, which promotes inflammation and cell division and is found in high levels in tumors. The Harvard study showed that people who tested positive for COX-2 benefited more from aspirin use than those without the enzyme. But Burn has another explanation for aspirin’s protective effect. He theorizes that aspirin targets faulty stem cells, destroying them before they mutate into pre-cancerous cells. “If aspirin reduced the chances of such cells surviving, this would explain our results,” he said.

Others aren’t convinced of Burn’s theory. “There’s something weird going on here that’s outside of what we normally see,” said Alfred Neugut of Columbia University Medical Center in New York, who has done similar work but was not involved in the European study. “Reducing cancer is a wonderful thing, but there is something else going on here that we don’t understand.”

Despite skepticism, Burn says the team is “delighted” with the study results, “all the more so because we stopped giving the aspirin after four years, yet the effect is continuing.” He said previous trials may not have been long enough to prove aspirin’s benefit, which is one reason their study targeted people with Lynch syndrome, because they who are likely to develop cancer more quickly. “The benefits are probably not seen in the general population for at least ten years,” he said.

Burn presented the study results in Berlin at a joint meeting of the European Cancer Organization and the European Society for Medical Oncology. The team’s future plans include a study to find out whether a lower dose of aspirin will also stave off colon cancer.

By: Madeline Ellis