Daily aspirin could help prevent and treat cancer: The Lancet

March 21, 2012

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Three new studies of using aspirin to prevent cancer, led by researchers at Oxford University, raise the possibility that a daily low dose of the drug could be effective, not just as a preventative measure, but as an additional treatment for those with cancer.

This follows the finding that aspirin can reduce the chances of tumors spreading to other parts of the body.

“We are not at the stage of recommending aspirin use in everybody, but the guidelines on use of aspirin in the healthy middle-aged population certainly need to be updated in order to take into account the effects on the risk and outcome of cancer as well as on the risk of heart attacks and strokes,” said Professor Peter Rothwell of the Nuffield Department of Clinical Neurosciences.

Previous studies by this team have established that aspirin reduces the long-term risk of dying from cancer, but that these effects don’t appear until about 8–10 years after starting taking a daily low dose of the drug. “What we have now shown is that aspirin also has short-term effects, which are manifest after only 2–3 years,” says Rothwell.

:In particular, we show that aspirin reduces the likelihood that cancers will spread to distant organs by about 40–50%. This is important because it is this process of spread of cancer or “metastasis” which most commonly kills people with cancer.”

This reduction in the risk of a cancer spreading suggests that starting taking aspirin after being diagnosed could be beneficial — assuming that the cancer has not already spread.

“No drug has been shown before to prevent distant metastasis and so these findings should focus future research on this crucial aspect of treatment of patients with cancer that hasn’t already spread. We argue in our papers that new trials are still required to confirm the benefit — but that such trials should be done urgently.”

The benefits of daily aspirin in reducing cancer risks are larger in absolute terms than the benefits in preventing heart disease and stroke, explains Professor Rothwell, particularly with prolonged use.

“In terms of preventing spread of cancer, the data suggest that the effect is largest in adenocarcinomas. These include cancers of the gut, particularly colorectal cancer, some cancers of the lung and most cancers of the breast and prostate. In terms of preventing the longer-term development of new cancers, the largest reductions are seen in risk of colorectal cancer and esophageal cancer, with smaller effects on several other common cancers.”

Shift in the balance of risks and benefits?

In any assessments of aspirin’s health benefits, it is important to take into account the increased risk of bleeding when taking the drug, particularly in the stomach.

The researchers report two new findings on the risk of stomach bleeds. They found that the extra risk of stomach bleeds due to aspirin falls with prolonged use — and so the risks of long-term treatment with aspirin — may well be less than previously thought.

The team also showed that the risk of a fatal stomach bleed is not increased on aspirin compared with placebo. In other words, the vast majority of people make a full recovery from the stomach bleeds caused by the aspirin. The conditions that aspirin helps to prevent, on the other hand, such as cancer, stroke and heart attacks, are much more likely to be disabling or fatal, the researchers argue.

Professor Rothwell says: ‘Previous analyses of the balance of risk and benefit have simply counted the crude numbers of bleeds and other outcomes, and have not considered the time-course of these risks or the severity of the different types of events.’

Taking low doses of aspirin is known to help prevent heart disease and stroke, and for this work on cancer the Oxford researchers used data from many of the trials establishing this effect. But among people that don’t have a heart problem already, the slight benefits of aspirin are largely balanced out by the increased risk of stomach bleeds.

The new information about aspirin and cancer could begin to change the overall assessment, the researchers believe.

Ref.: Peter M Rothwell et al., Short-term effects of daily aspirin on cancer incidence, mortality, and non-vascular death: analysis of the time course of risks and benefits in 51 randomised controlled trials, The Lancet, 2012 [DOI: 10.1016/S0140-6736(11)61720-0]

Ref.: Peter M Rothwell et al., Effect of daily aspirin on risk of cancer metastasis: a study of incident cancers during randomised controlled trials, The Lancet, 2012 [DOI: 10.1016/S0140-6736(12)60209-8]

Ref.: Annemijn M Algra and Peter M Rothwell, Effects of regular aspirin on long-term cancer incidence and metastasis: a systematic comparison of evidence from observational studies versus randomised trials, The Lancet, 2012 [DOI: 10.1016/S1470-2045(12)70112-2]

See also: Could a NOSH-Aspirin-a-Day Keep Cancer Away?, from The City College of New York.