Taking aspirin in your 40s could cut the risk of cancer developing later in life, according to research published in the Lancet Oncology.

In a detailed review of all the available evidence, Cancer Research UK scientists suggest that taking aspirin at an age before cancer begins to develop – and for at least 10 years – would maximise the drug’s potential to prevent cancer.

Previous research suggests that people who take aspirin are less likely to develop bowel, breast and possibly some other types of cancer. Aspirin blocks the effects of the COX enzymes, proteins involved in inflammation and found at unusually high levels in several types of cancer.

But regular use of the anti-inflammatory drug specifically for cancer prevention is not currently recommended as it has been linked to a number of side-effects including, gastrointestinal bleeding and stomach ulcers.

Common cancers, such as prostate, breast, lung and bowel, tend to develop after the age of 60. And the chances of aspirin causing bleeding in the abdomen are much higher in people over 60.

Study author, Professor Jack Cuzick, from the Cancer Research UK Centre for Epidemiology at Queen Mary, University of London, said: “Taking aspirin regularly in your mid 40s could maximise the effect this drug has on preventing cancer. Taking aspirin at this age, which is about the time pre-cancerous lesions usually begin to develop, may be the best time to stop the disease from progressing to actual cancer.

“And, as the risk of serious side effects of aspirin greatly increase after 60 years old, taking long-term treatment before this age will help to minimise these side effects.”

“But many questions need to be answered before we would advise regular use of aspirin for cancer prevention. Future research and more clinical trials are needed to better identify those people who are at high risk of developing cancers and at low risk of side effects, who will benefit most from aspirin treatment.”

“Some studies did not show a preventative effect, but the follow up was less than 10 years, so it may have been too early to see the effect.”

For older patients – who are already taking aspirin for cardiovascular disease – the drug may also provide additional protection against some cancers, but it not yet known whether the ‘baby aspirin’ can achieve this, or if the full standard dose of 300mg/day will be needed.”

The researchers also found that taking aspirin in combination with other drugs known as proton pump inhibitors could help to lower the risk of stomach bleeding. The AspECT trial, funded by Cancer Research UK, is investigating the use of proton pump inhibitors and aspirin in patients with Barrett’s oesophagus – a pre-cancerous condition that can develop into gullet cancer.

Dr Lesley Walker, Cancer Research UK’s director of cancer information, said: “We need scientists to focus their efforts on how to reduce the side effects of taking aspirin so that very soon it may be possible to use the drug as a way of preventing cancer. It’s too soon to recommend that people take aspirin to try and stop cancer developing because of the side effects. But, survival is low for cancers like gullet cancer so understanding how to prevent the disease is crucial. It’s important that any decision to take aspirin regularly is only made in consultation with a GP.”