Taking a low dose—81 mg—of aspirin every day is already recommended as a way to reduce the risk of heart disease and colorectal cancer in adults, aged 50 and older. Now, a recent study suggests that low-dose aspirin therapy may reduce the risk of certain subtypes of breast cancer. Although not conclusive, the study results were encouraging.
“The California Teachers Study has very promising data regarding the use of low-dose aspirin, but more studies are needed before pharmacists can routinely recommend this,” said Veronica Vernon, PharmD, Assistant Professor of Pharmacy Practice at Butler University College of Pharmacy and Health Sciences in Indianapolis. The observational study found that the risk of developing the HR-positive/HER2-negative subtype of breast cancer was lower among women who consistently took low-dose aspirin. While a 2008 meta-analysis of 38 studies found an association between a lower risk of breast cancer with aspirin and other anti-inflammatory drugs, this was the first study to suggest that low-dose aspirin might be more effective. One of the reasons aspirin is thought to reduce the risk is its ability to inhibit estrogen.
“Aspirin reduces inflammation, which may be one potential cause for breast cancer, as well as other types of cancer,” Vernon told Drug Topics. “In animal studies, aspirin blocked the conversion of normal cells to cancer cells. Aspirin acts as a mild aromatase inhibitor as well, as it lowers the amount of estrogen circulating in the blood.”
The study followed more than 50,000 women for more than 8 years, measuring factors such as hormone therapy, family cancer history, alcohol use, height, and weight. The study began collecting data in 1995 and by 2013, 1,457 cases of invasive breast cancer had been diagnosed in the study subjects.
The authors found that 23% of the women who took low-dose aspirin at least three times a week had a 20% reduction in developing HR-positive/HER2-negative breast cancer, but researchers did not find a similar result with regular full-dose aspirin use or other nonsteroidal anti-inflammatory medicines, such as ibuprofen. They did not draw any conclusions on why low-dose aspirin might be more effective.
Aspirin therapy is not suitable for everyone. “Gastrointestinal bleeding is the most concerning side effect,” said Vernon. “Aspirin may also lead to ulcer formation. Patients who have taken NSAIDs for an extended amount of time, consume three or more alcoholic beverages per day, or are over the age 65, may be at a higher risk of developing an adverse effect.”