A new American Cancer Society study finds men and women who used adult-strength aspirin (325 mg or more) daily for five or more years had an approximately 15 percent lower rate of developing any cancer than those who did not use aspirin.
The study, appearing in the Journal of the National Cancer Institute, finds specific cancers that occurred less commonly in long-term daily aspirin users included colorectal cancer, prostate cancer, and possibly breast cancer.
For their study, American Cancer Society researchers led by Eric J. Jacobs, PhD, addressed the potential effect of using adult-strength aspirin on overall cancer risk. A large study published by Harvard University researchers in 2005 found that taking a low-dose aspirin (about 100 mg) every other day did not lower risk of any cancer, suggesting that higher doses may be required to help prevent cancer. Adult-strength aspirin has been associated with reduced risk of colorectal cancer in previous studies, but this new study is the first to examine the relationship between long-term daily use of adult-strength aspirin and overall risk of cancer. Aspirin use was determined by a questionnaire.
During 12 years of follow up, nearly 18,000 men and women in the cohort were diagnosed with cancer. Those who reported daily use of adult-strength aspirin for at least five years had an approximately 15 percent relative reduction in overall cancer risk. The decrease was not statistically significant in women. The researchers looked at specific cancer sites and found men who used aspirin daily had a 20 percent lower risk of prostate cancer and that men and women who used aspirin had a 30 percent reduction in the risk of colorectal cancer. Aspirin use had no effect on the risk of other cancers studied: lung cancer, bladder cancer, melanoma, leukemia, non-Hodgkin lymphoma, pancreatic cancer, and kidney cancer. The researchers also found aspirin use for less than five years was not associated with decreased cancer risk.
"The American Cancer Society does not recommend using aspirin to prevent cancer because aspirin can cause serious gastrointestinal bleeding," said Dr. Jacobs. "Recommendations for aspirin use should continue to be based on prevention of heart disease and stroke, not cancer. However if further research confirms that daily adult-strength aspirin can meaningfully reduce cancer risk, future recommendations could take cancer prevention into account when deciding on the best dose for people who already need to take aspirin to prevent cardiovascular disease."