Does Aspirin Reduce Breast Cancer Risk? Which Mechanism Is Responsible?

A recently published study from a reliable cancer research center suggests that aspirin's breast cancer risk reduction does not work through estrogen (the female hormone), contrary to assumptions. However, this result may still depend on the aspirin doses used.

Breast cancer is the most common cancer in women. Approximately 227.000 women are diagnosed annually and around 40.000 die each year, making prevention a priority. Preventing or treating a disease requires understanding its mechanisms and those of preventive or therapeutic agents. Revealing mechanisms opens paths to many new solutions acting through them.

High estrogen levels are known to contribute to breast cancer. Reducing levels has therefore been adopted to lower risk, with regular exercise particularly effective. Many studies also found reduced risk with aspirin in postmenopausal women, thought to involve its effects on estrogen. A recent study, however, showed no effect on estrogen or estrogen-carrying proteins.

Healthy postmenopausal women aged 50-75, 144 in total, were divided into 2 groups. One received aspirin for 6 months at 325 mg daily. Estrogen measurements showed no effect. This produces 2 possibilities: either the estrogen effect is dose-dependent and these doses were ineffective, or breast cancer risk reduction involves a non-estrogen mechanism.

In conclusion, many reliable studies find that aspirin reduces breast and some other cancer risks. The mechanism remains unclear despite current attention to estrogen. No estrogen effect here suggests dose dependence or another mechanism. Both possibilities matter greatly for new preventive approaches, and more studies with different doses are needed. What is currently clear is that aspirin helps protect against some cancers and, if used for this purpose, must be taken only after consulting our doctor.