Recent randomised intervention trials have demonstrated that regular use of aspirin in patients with a history of colorectal adenoma (benign tumour) or cancer reduces the risk of recurrent adenoma within one to three years, according to background information in the article. However, whether long-term use of aspirin similarly reduces the risk of colorectal cancer and, if so, at what dose, has been unclear.

Andrew T. Chan, M.D., M.P.H., of Massachusetts General Hospital and Harvard Medical School, Boston, and colleagues examined the influence of aspirin and nonaspirin nonsteroidal anti-inflammatory drugs (NSAIDs) on the risk of colorectal cancer in a large group of women. The study included 82,911 women, enrolled in the Nurses’ Health Study.

Over the 20-year period, 962 cases of colorectal cancer were documented. Among women who regularly used aspirin (two or more standard [325-mg] tablets per week), there was a 23 percent reduced relative risk for colorectal cancer compared with nonregular users. However, significant risk reduction was not observed until more than ten years of use.

The benefit appeared related to dose: compared with women who reported no use, the relative risk for cancer was ten percent greater for women who used 0.5 to 1.5 standard aspirin tablets per week; eleven percent lower with two to five aspirin per week; 22 percent lower with six to 14 aspirin per week; and 32 percent lower with more than 14 aspirin per week. Women who took more than 14 aspirin per week for longer than ten years had a 53 percent lower relative risk for colorectal cancer. A similar dose-response relationship was found for nonaspirin NSAIDs.

“Our study supports a possible role for aspirin in cancer prevention, which has been demonstrated by prior adenoma recurrence trials. However, any substantial impact of aspirin on cancer necessitates early initiation and prolonged, consistent use,” the authors conclude.

MEDICA.de; Source: American Medical Association (AMA)