(HealthDay News) — Regularly taking low-dose aspirin appears to protect women from hormone receptor-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer, according to a study published online May 1 in Breast Cancer Research.

Christina Clarke, PhD, MPH, of the Cancer Prevention Institute of California in Fremont, and colleagues looked at the medication use of women enrolled in the ongoing California Teachers Study. That trial, begun in 1995, recruited 133,479 active and retired women teachers, administrators, and other public school professionals. In 2005, 57,164 participants answered questions about their use of aspirin and other medications, family history of cancer, use of hormone therapy, alcohol use, exercise, height, and weight. By 2013, 1,457 had developed invasive breast cancer.

Overall, the researchers found that use of low-dose aspirin at least 3 times a week was associated with a 16% reduced risk of breast cancer. But the more significant finding was the risk reduction for developing hormone receptor-positive/HER2-negative cancer. The researchers found a protective link with use of low-dose aspirin, but not with regular-dose aspirin or other nonsteroidal anti-inflammatory drugs such as ibuprofen or acetaminophen.

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“Our observation of reduced risk of breast cancer, among participants who took 3 or more tablets of low-dose aspirin weekly, is consistent with other reports looking at aspirin without differentiation by dose. This is the first report to suggest that the reduction in risk occurs for low-dose aspirin and not for regular-dose aspirin and only among women with the hormone receptor-positive/HER2-negative subtype,” the authors write. “This preliminary study builds on previous knowledge and further supports the need for formal cancer chemoprevention studies of low-dose aspirin.”

One author disclosed financial ties to Genentech/Roche.


  1. Clarke CA, Canchola AJ, Moy LM, et al. Regular and low-dose aspirin, other non-steroidal anti-inflammatory medications and prospective risk of HER2-defined breast cancer: the California Teachers Study. Breast Cancer Res. 1 May 2017. doi: 10.1186/s13058-017-0840-7