In a new study, researchers found that both aspirin and a purified omega-3, called EPA, reduce the number of pre-cancerous polyps in people at high risk of developing bowel cancer.
The study was led by the University of Leeds.
The team found that both aspirin and EPA reduced the number of bowel polyps in patients one year on from a screening colonoscopy (large bowel camera test), but they did not reduce the chances of an individual having any polyps present in the bowel.
Patients who took aspirin developed fewer polyps overall, including on the right side of the large bowel, the part which is most difficult to monitor by colonoscopy.
In addition, patients who took purified omega-3 EPA (eicosapentaenoic acid) also developed fewer polyps, but this effect was seen only on polyps on the left side of the bowel.
Bowel cancer remains the second largest cause of cancer deaths in the UK. Despite a national screening program, bowel cancer still resulted in over 16,000 deaths in England and Wales in 2014.
People at high risk of the disease are regularly monitored by specialists who use a flexible camera to examine the lining of the large bowel, also called the colon, by a technique called colonoscopy.
During a colonoscopy, a specialist looks for polyps, which are fleshy growths on the lining of the colon. The growths are usually benign but they can turn cancerous and so they are removed.
However, colonoscopy is not fool-proof and a significant number of people still continue to develop bowel cancer.
The current study was conducted to see if aspirin and EPA could provide another layer of prevention, alongside colonoscopy.
In the study, just over 700 people took part in from 53 hospitals in England, all of whom were identified as being at higher risk of developing bowel cancer after having a colonoscopy.
People who took part were randomly allocated to one of four treatment groups and, each day over the following year, they took either a 300 milligram aspirin tablet; 2 grams EPA in four capsules; a combination of both aspirin and EPA; or placebos only.
In the study, EPA is naturally present in fish oil, but was given to patients at a higher dose than is present in most omega-3 supplements that are available to the public.
Aspirin was provided by Bayer AG and EPA was partly provided by SLA Pharma AG.
The team found that patients who took aspirin had 22% fewer polyps at the end of the one year study compared to those who took the placebo.
Those who took EPA had 9% fewer polyps at the end of the study compared to those who took the placebo, although this difference was not statistically significant.
However, patients who took EPA had 25% fewer polyps in the left side of the bowel compared to those who took the placebo.
The team suggests that a ‘precision medicine’ approach may be the most appropriate way to use aspirin and omega-3 to prevent bowel polyps, in which patients at risk of particular types of polyps are given treatment specific to that risk.
They suggest that prevention is key in this common disease and the combination of widely available and relatively cheap drugs seemed to have such an impact.
Although aspirin and EPA had beneficial effects on polyp number on their own, the combination of aspirin and EPA together appeared to have an even greater effect.
However, the study was not designed to provide a definitive answer about combination treatment and further research is needed to test aspirin and EPA treatment together for polyp prevention.
Treatment with aspirin and EPA was safe with no increased bleeding risk seen. Individuals who took EPA on its own had a slight increase in stomach-upset symptoms.
The Lead author is Mark Hull, Professor of Molecular Gastroenterology at the University of Leeds.
The study is published today in The Lancet.
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Source: The Lancet.