Bowel cancer patients who take daily aspirin could cut their chance of dying from the disease by about a third, experts believe.

A study in the British Journal of Cancer looked at 4,500 bowel cancer patients living in The Netherlands.

All of the patients on aspirin were taking a low dose - 80mg or less a day - something already recommended for people with heart disease.

But experts say it is too soon to start routinely offering it for bowel cancer.

A wealth of evidence already suggests aspirin might prevent certain cancers from developing in the first place. And more recent work suggests it might also work as a cancer therapy - slowing down or preventing a cancer's spread.

Anyone thinking of taking aspirin to cut their risk of cancer should talk to their GP first Sarah Lyness, Cancer Research UK BBC Health: Bowel cancer symptoms

But the drug can also have unpleasant and dangerous side effects, causing irritation of the stomach lining and internal bleeds in a very small minority of patients.

The findings

In the study, which spanned nearly a decade, a quarter of the patients did not use aspirin, a quarter only took aspirin after being diagnosed with bowel cancer, and the remaining half took aspirin both before and after their diagnosis.

Most of the patients on aspirin had been taking it to prevent cardiovascular disease-related problems like stroke or heart attack.

Taking aspirin for any length of time after diagnosis cut the chance of dying from bowel cancer by 23%.

The patients who took a daily dose of aspirin for at least nine months after their diagnosis cut their chance of dying from the disease by 30%.

Taking aspirin only after bowel cancer had been detected had a bigger impact on reducing mortality compared with when aspirin was taken before and after diagnosis - reducing death risk by 12%.

This may be because those who took aspirin and still got bowel cancer had a particularly aggressive form of tumour that did not respond as well to aspirin, say the researchers.

Aspirin Also known as acetylsalicylic acid

Used for many years as a painkiller

Has an anti-inflammatory action

Low-dose (75mg) is already recommended for people with known cardiovascular disease to prevent stroke and heart attack

Benefits for healthy people are still unclear

Can cause fatal internal bleeding, although this is relatively rare

Lead researcher Dr Gerrit-Jan Liefers, of the Leiden University Medical Centre, said: "Our work adds to growing evidence that aspirin not only can prevent cancer from occurring but if it is there it can help prevent it spreading."

He said aspirin should not be seen as an alternative to other treatments, such as chemotherapy, but could be a useful additional treatment.

"It's possible that some older people may have other health problems which mean that they are not well enough to have chemotherapy. Bowel cancer is more common in older people so these results could be a big advance in treatment of the disease, particularly in this group. But we need further research to confirm this."

He said they now planned to hold a randomised controlled trial - the "gold standard" in medical research - to look at how well aspirin fared against a dummy drug in people aged over 70 with bowel cancer.

Sarah Lyness of Cancer Research UK said: "This latest study adds to the growing evidence about the benefits of aspirin.

"But we are not yet at the point where we would recommend people start taking aspirin to reduce their chances of developing cancer.

"There are still questions we need to answer about the side effects, such as internal bleeding, who might benefit most from taking aspirin, who might be harmed, what dose and how long people some people might want to take it for.

"Anyone thinking of taking aspirin to cut their risk of cancer should talk to their GP first. People with cancer should be aware that aspirin can increase the chances of complications before surgery or other cancer treatments such as chemotherapy, and should discuss this with their specialist.

"In the meantime, there are many ways we can take to lower our risk of developing cancer - not smoking, cutting back on alcohol and keeping a healthy weight can help stack the odds in our favour."