Dr. J Cuzick from the Queen Mary University of London and international colleagues from several institutions performed a review of studies linking the use of aspirin to decreased risk of several types of cancer and of heart attacks and stroke. Their study was published in the Annals of Oncology.
The investigators pointed out that while aspirin can have serious side effects, most commonly gastrointestinal bleeding, accumulating scientific data suggest that it may also be useful in preventing several types of cancer when taken long-term. Thus they estimated the overall benefits and risks of using aspirin for long-term prophylaxis of various forms of cancer. Included in their review were randomized studies (participants are randomly assigned to receive aspirin or a placebo) as well as case-control (aspirin use by people with and without various types of cancer or cardiovascular events are compared) and prospective cohort studies (participants are followed for various periods and queried about their use of aspirin as well as their diagnoses).
In general, the effects of aspirin on cancer were not apparent until after at least 3 years of use. In particular, the risk of new cases of colorectal, esophageal and gastric cancer were reduced by 30-35 percent, and the risk of death from those diseases was also reduced by 30 to 45 percent. The risk of heart attack was decreased by 18 percent, while that of stroke was decreased by about 5 percent. However, the risk of dying from a stroke was increased by about 20 percent in those who used aspirin.
On the other side of the equation, the risks of an adverse event associated with aspirin use rose as the participants ages increased. For example, the risk of any major extracranial bleeding (especially GI bleeding) in men and women aged 60-64 was increased by 12 percent in men and decreased by 44 percent in women; and this elevated risk increased even further in the older age groups.
One uncertainty the authors noted was the possible carry-over benefit once aspirin use is terminated. They found that the effects on cancer mortality persisted for several years after the end of 5-9 year randomized trial, but made the point that it wasn t clear to what extent participants continued using aspirin. In addition, they said There is also uncertainty about whether there is an upper age at which the harms outweigh the benefits.
Thus commented ACSH s Dr. Gilbert Ross, before anyone begins to use aspirin prophylactically, he or she should discuss with their physician the likely risks and benefits based on their own history and risk factors. He continued For example, a person with a history of GI bleeding or an ulcer should probably be advised against using aspirin to prevent cancer.