Low-dose aspirin might lower breast cancer risk
By Ilene Schneider
While we extol the virtues of low-dose aspirin, there may be yet another reason to do so. An article in the journal, Breast Cancer Research, suggests that the frequent use of low-dose aspirin may cut the risk of breast cancer.
The California Teachers Study involved 57,000 women. The 23 percent of them who used low-dose aspirin at least three times a week had a 20 percent reduced risk for HR-positive/HER2 negative breast cancer, a frequent form of the disease. Other non-steroidal anti-inflammatory drugs, like Ibuprofen, did not produce this result, and neither did high-dose aspirin.
Aspirin is thought to lower the risk for colorectal cancer, and, of course, it is well known for reducing the risk of cardiovascular disease by lowering the platelet count, keeping coronary arteries open and letting the heart work less hard. The U.S. Preventive Services Task Force advises that low-dose aspirin should be used to reduce the risk of both heart disease and colorectal cancer.
Study leader Leslie Bernstein is a professor in the Division of Cancer Etiology in the Department of Population Sciences at the Beckman Research Institute, which is a branch of the City of Hope Comprehensive Cancer Center in Duarte, California. She described her findings as "moderate" reduction in risk, "maybe not as good as exercise," but she thinks that more people might adhere to an aspirin regimen than an exercise routine.
Dr. Bernstein says that the anti-inflammatory property of aspirin may be what is behind the apparent reduction in breast cancer risk. “Simply, things like obesity or inflammatory conditions are a risk factor for breast cancer, so this may be the one reason it could help,” Bernstein said. She also noted that aspirin inhibits the enzyme aromatase. Anti-cancer drugs used against breast cancer are also aromatase inhibitors. Estrogen increases the growth of hormone receptor-positive breast cancer cells, and aspirin helps to block estrogen.
This study, which did not include clinical trials, is not definitive. “Of course, more research, including clinical trials, is needed to see if this is the case,” Dr. Bernstein concluded.
Less optimistic is Professor Nancy Cook of the Department of Epidemiology at Harvard University. She led a 2013 study on the effects of low-dose aspirin. Her study confirmed the impact of aspirin on reduced colorectal cancer rates but did not see any breast cancer reduction.
“It is possible that the lack of effect is due to the alternative day low dose that we used, but data from other randomized trials generally do not support an effect on breast cancer,” Professor Cook said.
Because the new study is only observational, “that means it cannot determine cause and effect. The meta-analyses that the authors cite are also mainly based on observational data. On the other hand, large observational studies sometimes are able to detect effects in some groups or for more rare outcomes that trials are not empowered to see, so these studies are still valuable,” Professor Cook concluded.