A large meta-analysis, published in May 2017 by my colleagues at the City of Hope (COH) Comprehensive Cancer Center, indicates that consistent ingestion of low-dose aspirin may play a role in the prevention of hormone receptor–positive (HR+)/human epidermal growth factor receptor 2 (HER2)-negative breast cancer. The authors compared women who took regular-dose (325 mg) aspirin or used another type of nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen, with those who consumed low-dose aspirin (81-mg tablets, also known as “baby” aspirin) at least three times a week. They found that the low-dose aspirin users had 20% lower risk of developing HR-positive/HER2-negative breast cancer, which is one of the most common breast cancer subtypes.1
The study, published online in Breast Cancer Research, was led by Christina A. Clarke, PhD, MPH, from the Cancer Prevention Institute of California. The data are derived from the California Teachers Study, a prospective cohort established in 1995–1996 with more than 133,000 teachers and public school professionals registered. The study participants completed a baseline health-and-medications questionnaire, and at 10-year follow-up in 2005–2006 more than 57,000 women answered questions about height and weight; living environment and physical activity; diet and current use of alcohol; cancer history; menstrual and child-bearing history; and medication use, including low-dose and regular-dose aspirin as well as ibuprofen and other NSAIDs.2
From the time of 10-year follow-up to December 31, 2012, about 1,400 of the 57,000 women had developed breast cancer, and 68% of the cases were HR-positive/HER2-negative. Besides the 20% reduced risk of HR-positive/HER2 negative breast cancer observed, there was a 16% reduction in risk of any type of breast cancer in the women who used low-dose aspirin at least three times a week. There were no significant benefits associated with use of regular-dose aspirin or other types of NSAIDs.
One reason for the study results may be that aspirin can reduce inflammation. “Simple things like obesity or inflammatory conditions are a risk factor for breast cancer, so this may be one reason [aspirin] could help,” said senior study author Leslie Bernstein, PhD, Director of the Division of Cancer Etiology at COH and professor of medicine at its Beckman Research Institute.2
While the current study does not establish a cause-and-effect relationship, it is the first to suggest that a reduction in breast cancer risk occurs for low-dose but not regular-dose aspirin, and only among women with the hormone receptor-positive/HER2-negative subtype. It is possible that the protective benefits were not seen at the regular 325-mg aspirin dose because regular aspirin is taken only sporadically for headaches or other pain, whereas low-dose aspirin is typically consumed daily for prevention of cardiovascular disease, Dr. Clarke said.2
Few studies have evaluated the chemopreventive effect of aspirin on the risk of cancer in elderly women. In the Iowa Women’s Health Study, investigating a prospective cohort of women over 70 years of age, the frequency, dose, and duration of aspirin use were found to be associated with the incidences of cancers of the colon, pancreas, breast, and ovaries.3 However, further studies are required for validation.
At our weekly tumor board discussions, we have just begun to explore the possible chemopreventive effects of aspirin, although no formal institutional review board studies have been initiated at this time. Although the current study by Dr. Clarke and colleagues builds on previous knowledge, additional formal cancer chemoprevention studies of low-dose aspirin are warranted.4
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. 2017;19:52.
2. Study suggests link between low-dose aspirin and lower risk for specific type of breast cancer [news release]. Breastcancer.org; May 4, 2017. http://www.breastcancer.org/research-news/link-between-aspirin-and-lower-risk Accessed October 4, 2017.
3. Lu L, Shi L, Zeng J, Wen Z. Aspirin as a potential modality for the chemoprevention of breast cancer: a dose-response meta-analysis of cohort studies from 857,831 participants. Oncotarget. 2017;8:40389-40401.
4. Vaughan LE, Prizment A, Blair CK, Thomas W. Aspirin use and the incidence of breast, colon, ovarian, and pancreatic cancers in elderly women in the Iowa Women’s Health Study. Cancer Causes Control. 2016;27:1395-1402.