Overall risk of dying from cancer was reduced by 16% among people who took daily dose of aspirin when healthy

Taking a low dose of aspirin every day may reduce the risk of cancer and slow the spread of the disease, according to a study that followed the health of more than 100,000 patients.

Research by a team at the American Cancer Society in Atlanta found the overall risk of dying from cancer was 16% lower among people who took a daily aspirin pill for up to 11 years, with deaths from gastrointestinal cancers, such as oesophageal, stomach and colorectal cancers, falling by around 40%. Deaths from other cancers fell by 12% on average.

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The findings, based on 100,139 men and women with no prior history of cancer, support previous claims that aspirin can protect against some forms of the disease, but suggest the effect is not as strong as those earlier studies found.

In research published in March, Peter Rothwell at Oxford University reported that the risk of dying from cancer was around 37% lower for people who took aspirin for more than five years. Those who had a daily dose of the drug for three years reduced their risk of cancer by about a quarter, his study found.

The latest work, led by cancer scientist Eric Jacobs, points to a more modest protective effect from aspirin, though the authors concede that the design of the study may have led them to over- or underestimate the drug’s anti-cancer properties.

“Even a relatively modest benefit with respect to overall cancer mortality could still meaningfully influence the balances of risk and benefits of prophylactic aspirin use,” the authors write in the Journal of the National Cancer Institute. Aspirin did not reduce lung cancer among smokers, suggesting that cigarette smoking negated its benefits.

Scientists are unsure how aspirin prevents cancer, but it may act by damping down inflammation in the body, or slowing the buildup of mutations in cells that ultimately turn cancerous. The drug appears to slow the spread of cancer around the body by preventing cancer cells from sticking to blood platelets.

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Despite the evidence that regular low doses of aspirin – 75mg a day – can keep cancer at bay, many doctors believe it is too early to encourage widespread use of the drug to prevent the disease. One of the most serious side effects of aspirin is damage to the stomach lining. This can cause internal bleeding, which in rare cases is fatal, especially in those aged 70 and older.

“Although recent evidence about aspirin use and cancer is encouraging, it is still premature to recommend people start taking aspirin specifically to prevent cancer. Even low-dose aspirin can substantially increase the risk of serious gastrointestinal bleeding,” said Jacobs.

He added: “Decisions about aspirin use should be made by balancing the risks against the benefits in the context of each individual’s medical history. Any decision about daily aspirin use should be made only in consultation with a health care professional.”

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In an accompanying editorial, John Baron, a clinical epidemiologist at the University of North Carolina in Chapel Hill, wrote: “This is exciting: simply taking a pill can prevent cancer incidence and cancer death. However, just because aspirin is effective does not mean it necessarily should be used. Aspirin is a real drug, with definite toxicity. As for any preventative intervention, the benefits must be balanced against the risks, particularly when the benefits are delayed whereas the risks are not.”

© Guardian News and Media 2012

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[Taking pills detail via Shutterstock.com.]