Inexpensive drugs, aspirin and a purified omega-3 called EPA, can reduce the number of pre-cancerous polyps in patients found to be at high risk of developing bowel cancer, according to a study released Tuesday by the University of Leeds.

Both aspirin and EPA showed promise in reducing the number of bowel polyps in patients one year on from a screening colonoscopy in a clinical trial led by researchers from the University of Leeds.

Patients who took aspirin developed fewer polyps overall, while those who took EPA also developed fewer polyps, but this effect was seen only on polyps on the left side of the bowel, which is nearest the rectum.

People at high risk of bowel cancer are regularly monitored by specialists who use a flexible camera to examine the lining of the large bowel, which is called colonoscopy.

During a colonoscopy, a specialist looks for polyps, which are fleshy growths on the lining of the colon. The growths are usually benign but they can turn cancerous and so they are removed.

The trial "demonstrates that both aspirin and EPA have preventative effects, which is particularly exciting given that they are both relatively cheap and safe compounds to give to patients", said Lead author Mark Hull, Professor of molecular gastroenterology at the University of Leeds.

The study has been published in the journal The Lancet.