Low-dose aspirin might help fend off breast cancer, according to a new study.

Researchers at the City of Hope Comprehensive Cancer Center noted an overall 16 percent reduction in breast-cancer risk among the 57,000 women who took an 81-milligram dose of aspirin three or more times a week.

The most striking finding, according to researchers, was the effect the aspirin had on the most common form of breast cancer, known as estrogen or progesterone receptor positive HER2-negative breast cancer. The risk of developing that subtype was reduced by 20 percent.

The participants, part of the California Teachers Study that began in 1995, filled out questionnaires that included their exercise, smoking and drinking habits, family history of cancer and medications they took, including hormone replacement therapy.

By 2013, almost 1,500 women reported having developed invasive breast cancer. 

The reduction in breast cancer risk in the City of Hope study was seen in comparison to the results of other large studies investigating the possible benefits of higher-dose aspirin and other painkillers. The study’s findings were published online in the journal Breast Cancer Research.

Investigators did not see a breast-cancer risk reduction among women who took regular-strength aspirin or other types of painkillers. They said that may be because some women only took the aspirin occasionally, for pain relief.

Low-dose aspirin taken regularly has been linked to other health benefits, including reductions in the risk of heart disease and colon cancer.

Investigators in the latest study only found an association, not a causal link, between the use of baby aspirin and a reduced risk of breast cancer.

Researchers noted aspirin reduces inflammation, which plays a role in the initiation of disease. They also said the painkiller is a mild aromatase inhibitor. Aromatase inhibitors reduce the amount of the female hormone estrogen circulating in the bloodstream, which fuels breast tumors, so they are used to treat some forms of breast cancer in post-menopausal women.

At this point, researchers are not recommending that women start taking low-dose aspirin to protect themselves against breast cancer. They said more research is needed showing a definite link between baby aspirin and cancer prevention.
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