Studies in animals have also shown that this drug is likely to prevent colorectal polyps and cancer

Dr Wendy Atkin

Polyps, or growths, on the lining of the bowel affect around one in five people.

While most never become malignant they are usually removed because, in a minority of cases, they can become cancerous.

Following surgery, patients are given regular checks every three to five years because the polyps can return.

Enzyme

Celecoxib inhibits the body's production of an enzyme called COX-2.

COX-2 is typically produced by the body when there is inflammation.

But it is also produced by pre-cancerous tissues, such as polyps.

It is hoped that blocking this enzyme production may help to block the development of cancer.

Dr Wendy Atkin, Deputy Director of Imperial Cancer Research Fund's Bowel Cancer Unit and UK co-ordinator of the celecoxib trial, said: "Celecoxib is a drug that is similar to aspirin, but with fewer side effects.

"It has already shown to prevent polyps in people with a condition known as familial adenomatous polyposis (FAP) who have a very high risk of getting bowel cancer.

"Studies in animals have also shown that this drug is likely to prevent colorectal polyps and cancer."

Participants will take either the celecoxib or placebo drug for three years.

Dr Atkin said: "We will have to wait until the study's completion in around three years to judge whether the drug will be useful in preventing recurrent bowel polyps in people who have already had one polyp removed."

Evidence

Dr Mary Berrington, of the Cancer Research Campaign, said there was already evidence that regular use of 'non-steroidal' anti-inflammatory drugs could help reduce the risk of bowel polyps and bowel cancer - but that it was not yet conclusive.

She said: "This is an important trial. Many bowel cancers are diagnosed at a late stage when treatment is difficult, so finding ways of preventing the disease is a top priority."

Bowel cancer kills more people than any other type of cancer apart from lung cancer. Around 30,000 people are diagnosed with it every year.

A diet high in fibre can help to reduce the risk of developing the disease.