Aspirin cuts hereditary bowel cancer risk by 60 percent

Taking a daily aspirin has been recommended for people with a high risk of an inherited form of bowel cancer. Results published in the Lancet suggested the risk for those with Lynch syndrome could be cut by 63 percent.

Professor Sir John Burn, of Newcastle University, who led the study, told the BBC that the evidence 'seems overwhelmingly strong'.

A daily low dose of aspirin is prescribed to people at risk of heart attack or stroke, and some researchers had noticed that these groups showed lower rates of colorectal cancer. The Colorectal Adenoma/carcinoma Prevention Programme (CAPP2) study — the first double-blind, randomised controlled trial of aspirin focusing on the prevention of cancer — confirmed it could have a dramatic effect on the development of colorectal tumours.

'People who've got a clear family history of, particularly, bowel cancer should seriously consider adding low dose aspirin to their routine and particularly those people who've got a genetic predisposition', Professor Burn recommended.

Lynch syndrome, or hereditary nonpolyposis colorectal cancer (HNPCC), is an inherited form of colorectal cancer caused by genetic mutations, which around one in 1,000 people carry. Around 90 percent of men and 70 percent of women with HNPCC will develop bowel cancer by the age of 70. They are also at risk of other cancers, such as cancer of the uterus, ovary, breast, prostate, brain, pancreas, gall bladder, ureter, stomach and kidney.

Participants in the CAPP2 trial took 600 mg of either aspirin or placebo daily between 1999 and 2005. The 861 patients were followed for up to ten years at 43 centres across 16 countries.

Data in 2007 showed no difference between the two groups, but an assessment in 2010 showed that while 34 people had developed new colorectal cancers in the placebo group, there were only 19 new cancers in the aspirin-treated group. Furthermore, it found that there was an overall reduction in other cancers — 23 in the placebo group, and only 10 in the aspirin group.

Based on these results, giving aspirin to people at risk could prevent up to 10,000 cancers over the next decade, which could save up to 1,000 lives. As people in the study taking aspirin showed no more adverse effects than those taking placebo, this could be a safe and cost-effective way of preventing cancer.

Taking aspirin is not risk-free, as it can increase the risk of ulcers and bleeding in the gut in some people, but, as Professor Burn commented: 'If we can prevent 10,000 cancers in return for 1,000 ulcers and 100 strokes, in most people's minds that's a good deal'.

It is unclear quite how aspirin works — it may be through its role as a COX2 inhibitor, it could act to kill of cells in the early stages of the cancers or even by destroying the stem cells that are likely to differentiate into cancer cells.

Further work will come in the form of CAPP3, a trial to optimise the dose and duration of the treatment with aspirin.