A condition called familial adenomatous polyposis, usually shortened to FAP, puts people at very high risk of bowel cancer. This condition, which runs in families, means people get lots of small, fleshy growths (called polyps) on the inner surface of their bowel. If left, these growths are likely to turn into cancer.
Most people with FAP need to have sections of bowel removed by surgery, to prevent their bowel becoming cancerous. Ideally, surgeons like to leave people with as much of their bowel as possible, including the rectum (the end nearest the anus), so they don't need to have a permanent colostomy bag. People who've had a section of bowel removed need regular checking of their rectum (by a process called endoscopy) to monitor the growth of new polyps.
Some people with FAP take an anti-inflammatory drug, called celecoxib, which slows the growth of new polyps. But celecoxib may increase the risk of having a heart attack, so doctors are cautious about using it in the long term, especially for older people.
Studies in mice have shown that a type of purified fish oil, called eicosapentaenoic acid (EPA for short), may work in a similar way against bowel cancer. So, doctors want to see if it could be used instead of celecoxib for people with FAP.