People at high risk from developing cancer of the rectum or colon should start taking between four and six aspirin a week, new research has suggested. A low-dose aspirin regime using 325 mg each time could cut the risk of colorectal cancer by half in
Unfortunately, these benefits only start becoming apparent after 10 years of consistent use, and risks are halved only after taking aspirin for 20 years.
People who take aspirin run the risk of suffering stomach bleeding, but doctors say this is far outweighed by the benefits among high-risk groups, which include sufferers of inflammatory bowel disease, breast, ovarian or endometrial cancers, or a previous adenoma or large-bowel cancer.
Others considered in a high-risk group are those whose family has a history of colorectal cancer.
These findings are based on the major Nurses' Health Study, which has tracked the health of 121,701 nurses in the US since 1976 who have a known or suspected risk of developing breast cancer or heart disease.
Researchers discovered that the women who consistently took four to six aspirin a week from 1984 to 1992 halved the risk of developing the cancer, and the risk continued to fall as the dosage increased, although cases of bleeding were reported in women who took more than 14 aspirin a week. Women who took two aspirin a week only saw a noticeable reduction of risk after 20 years; after four years' usage at these levels, there was virtually no benefit at all.
Although the research involves only women, researchers say the same benefits should be experienced by men.
Researchers believe that aspirin indirectly blocks tumour growth, although they also accept that other factors could have been at play. They recommend that specific, long-term research is carried out to check their own findings (N Eng J Med, September 7, 1995).