The study showed that taking 300mg of aspirin a day for five years could reduce the incidence of colorectal cancer by 37 per cent, and by 74 per cent during a period of 10–15 years after treatment was started.
But potential risks associated with the long-term use of high-dose aspirin suggest that screening remains the best option to prevent colorectal cancer, experts say.
For the study, researchers determined the delayed effect of aspirin by following up 7,582 patients from two large randomised trials of aspirin performed in the late 1970s and early 1980s.
The long-term study was necessary because the pre-cancerous growths that aspirin is thought to reduce take at least 10 years to develop into cancers.
The effects of aspirin were found to be consistent regardless of age, sex and race.
Lead researcher Peter Rothwell, professor of neurology at the University Department of Clinical Neurology, Radcliffe Infirmary, Oxford, said GPs should advise patients at high risk, such as those with a strong family or personal history of colorectal cancer, to take 300mg of aspirin daily.
‘It is important for GPs to take this proven additional benefit of aspirin into account in the choice of anti-platelet drug in patients who need to take anti-platelet drugs for vascular disease.’
However, the risks of long-term treatment with aspirin might still outweigh the benefits in individuals at low-risk of colorectal cancer, Professor Rothwell said.
‘The benefits in individuals at low risk of colorectal cancer will be small.’
West London GP Dr Sarah Jarvis, a member of the Primary Care Cardiovascular Society, said that she had real concerns about giving patients such a high daily dose of aspirin.
‘Taking 300mg of aspirin daily can cause GI bleeding. One in 2,000 people on high-dose aspirin will suffer a fatal bleed, while just one in 248 will experience some GI bleeding.’
It would be far better for GPs to promote the NHS colorectal cancer-screening programme, because it is a much better and safer way to prevent the disease, Dr Jarvis said.
If patients with an increased risk of colorectal cancer are to be given high-dose aspirin, then more research is required to assess the full benefits of the treatment, she added.
What do you think? Comment below or email us at GPletters@haymarket.com