Prophylactic aspirin therapy of at least 5 years’ duration has a favorable benefit-harm profile, primarily because of its effectiveness in preventing colorectal and other cancers, according to a report in the August issue of Annals of Oncology.
In a review and summary of the current evidence regarding the benefits and harms of aspirin therapy, investigators analyzed the protective and adverse effects of several dosing regimens for both men and women at four different ages: 50, 55, 60, and 65 years. Their analysis assumed (conservatively) that protection against cancer begins 3 years after starting aspirin and continues for 5 years after stopping it, said Jack Cuzick, Ph.D., of the center for cancer prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, and his associates.
Courtesy Public Relations for the School of Medicine and Dentistry at Queen Mary University of London
Dr. Jack Cuzick of the Wolfson Institute of Preventive Medicine, Queen Mary University of London, reported benefits of aspirin.
The researchers found "overwhelming" evidence that aspirin therapy reduces the incidence of colorectal cancer by approximately 30% and mortality from the disease by approximately 40%. It is effective in both men and women, in every age group, at every dosage, and in patients at high risk for colorectal cancer.
Prophylactic aspirin is also effective in reducing mortality related to esophageal cancer by 27%-58%, depending on the study. It exerts "substantial" protection against stomach and other gastric cancers, but does not appear to do so with pancreatic cancer. Aspirin therapy exerts a smaller protective effect against breast, prostate, lung, and endometrial cancers, Dr. Cuzick and his associates said.
These benefits are seen in both men and women, as well as in all age groups studied. But absolute benefits are greatest among older men.
Prophylactic aspirin also reduces serious cardiovascular events, particularly nonfatal myocardial infarction, to a much smaller degree.
"Using our ‘best estimates’ for individuals taking aspirin for 10 years, there would be a relative reduction of approximately 9% in the number of men and 7% in the number of women with a cancer, MI, or stroke event over a 15-year period," the investigators said (Ann. Oncol. 2014 Aug. 5 [doi:10.1093/annonc/mdu225]).
"Reductions in cancer incidence would account for 61%-80% of the overall benefit, and reductions in colorectal cancer alone would account for 30%-36% of it," they noted.
It is still uncertain whether there is an upper age limit at which potential harms, such as excess bleeding, outweigh potential benefits, and the optimal dose for cancer prevention hasn’t yet been established, the authors added.
This study was sponsored by the International Society of Cancer Prevention, Cancer Research U.K., the British Heart Foundation, and the American Cancer Society. Dr. Cuzick reported serving on an advisory board for Bayer; several associates reported ties to numerous industry sources.