Bowel and colon cancer reduced by aspirin

TAKING LOW-DOSE aspirin long-term reduces the incidence of colon cancer by a quarter, research published this morning shows.

Researchers from Oxford University carried out the first study to assess the long-term effectiveness of aspirin on colorectal cancer incidence and mortality and report their results in The Lancet.

Prof Peter Rothwell and his colleagues performed a 20-year follow-up of four randomised trials which were originally conducted to assess the cardiovascular benefits of aspirin.

By pooling data from the trials they were able to follow up more than 14,000 people from the UK and Sweden who had taken between 75mg and 300mg of aspirin for 18 years on average. The analysis showed aspirin reduced the 20-year risk of colon cancer by 24 per cent and mortality from bowel cancer by 35 per cent.

Significantly they found the reduction in the number of cases of bowel cancer and deaths from the disease were almost entirely due to fewer cancers growing in the proximal large bowel. This is the part of the large bowel furthest away from the rectum; it commences where the small bowel ends. It is also the part of the large bowel that is hardest to reach when a patient undergoes a colonoscopy to check for growths.

These findings suggest a complementary role for bowel cancer screening and chemoprevention using a long-term daily dose of 75mg of aspirin.

“The suggestion of a particular effect of aspirin on more aggressive and rapidly growing tumours might allow less frequent screening, and the prevention of proximal colonic cancers by aspirin, which would not be identified by sigmoidoscopy [an examination of the distal bowel], is clearly important. It is therefore probable that these two approaches to prevention of colorectal cancer will be synergistic,” the authors note.

Most colorectal cancers develop from benign polyps and screening programmes reduce the incidence of bowel cancer by removing these early growths.

“Our findings suggest that long-term low-dose aspirin treatment and sigmoidoscopy screening would combine to substantially reduce cancer incidence in all parts of the colon and rectum,” Prof Rothwell said.

Colorectal cancer is the second most common cancer in developed countries, with a lifetime risk of 5 per cent. Latest figures from the National Cancer Registry show in excess of 2,200 colorectal cancers are diagnosed in the Republic annually. About 1,000 people die from the disease here each year.

Minister for Health Mary Harney has announced plans to commence a national colorectal cancer screening programme in 2012.