The use of low-dose aspirin reduced the risk of breast cancer in women who are part of the California's Teacher's Study.
This study – which is the first to suggest that the reduction in risk occurs for low-dose aspirin (81mg) – was proposed by City of Hope's Dr Leslie Bernstein, professor and director of the division of biomarkers of early detection and prevention.
Bernstein and her colleagues saw an overall 16% lower risk of breast cancer in women who reported using low-dose aspirin at least three times per week. Such regular use of low-dose aspirin reduced the risk by 20% of oestrogen or progesterone receptor positive, HER2 negative breast cancer, which is the most common breast cancer subtype.
"The study found an interesting protective association between low-dose aspirin and breast cancer," said lead author Dr Christina A Clarke, from the Cancer Prevention Institute of California. "We did not by and large find associations with the other pain medications like ibuprofen and acetaminophen. We also did not find associations with regular aspirin since this type of medication is taken sporadically for headaches or other pain, and not daily for prevention of cardiovascular disease."
This study differed from other studies that have looked at aspirin and cancer risk because it focused on the dose levels of the aspirin women had taken and tracked the frequency of the use of low-dose aspirin as opposed to regular aspirin. It was also able to look in detail at subtypes of breast cancer.
"We already knew that aspirin is a weak aromatase inhibitor and we treat women with breast cancer with stronger aromatase inhibitors since they reduce the amount of oestrogen post-menopausal women have circulating in their blood," said Bernstein. "We thought that if aspirin can inhibit aromatase, it ought to reduce the likelihood that breast cancer would develop and it could also be an effective way to improve breast cancer patients' prognosis once they no longer take the more potent aromatase inhibitors."
Bernstein added, "Aspirin also reduces inflammation, which may be another mechanism by which aspirin taken regularly can lower risk of breast cancer developing or recurring."
As part of the study, researchers analysed data recorded in questionnaires submitted by 57,164 women in the California's Teacher's Study. In 2005, participants answered questions regarding family history of cancer and other conditions, use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDS), menstrual and reproductive history, use of hormones, weight and height, living environment, diet, alcohol use and physical activity. In the ensuing years before 2013, 1,457 of these participants developed invasive breast cancer.
The team of researchers chose to focus on low-dose "baby" aspirin, because not only is it inexpensive and readily available as potential means of prevention, but because there are already a lot of people already taking it for prevention of other diseases such as heart disease and even colon cancer.
Now that we have some data separating low-dose from higher-dose aspirin, more detailed research can be undertaken to understand the full value of low-dose aspirin for breast cancer prevention," said Clarke."
Abstract
Background: Regular users of aspirin may have reduced risk of breast cancer. Few studies have addressed whether risk reduction pertains to specific breast cancer subtypes defined jointly by hormone receptor (estrogen and progesterone receptor) and human epidermal growth factor receptor 2 (HER2) expression. This study assessed the prospective risk of breast cancer (overall and by subtype) according to use of aspirin and other non-steroidal anti-inflammatory medications (NSAIDs) in a cohort of female public school professionals in California.
Methods: In 1995 − 1996, participants in the California Teachers Study completed a baseline questionnaire on family history of cancer and other conditions, use of NSAIDs, menstrual and reproductive history, self-reported weight and height, living environment, diet, alcohol use, and physical activity. In 2005–2006, 57,164 participants provided some updated information, including use of NSAIDs and 1457 of these participants developed invasive breast cancer before January 2013. Multivariable Cox proportional hazards regression models provided hazard rate ratios (HRR) for the association between NSAID use and risk of invasive breast cancer as well as hormone receptor- and HER2-defined subtypes.
Results: Developing breast cancer was associated inversely with taking three or more tablets of low-dose aspirin per week (23% of participants). Among women reporting this exposure, the HRR was 0.84 (95% confidence interval (CI) 0.72–0.98) compared to those not taking NSAIDs and this was particularly evident in women with the hormone receptor-positive/HER2-negative subtype (HRR = 0.80, 95% CI 0.66–0.96). Use of three or more tablets of “other” NSAIDs was marginally associated with lower risk of breast cancer (HRR = 0.79, 95% CI 0.62–1.00). Other associations with NSAIDs were generally null.
Conclusion: Our observation of reduced risk of breast cancer, among participants who took three 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. This preliminary study builds on previous knowledge and further supports the need for formal cancer chemoprevention studies of low-dose aspirin.
Authors
Christina A Clarke, Alison J Canchola, Lisa M Moy, Susan L Neuhausen, Nadia T Chung, James V Lacey, Leslie Bernstein
[link url="https://www.sciencedaily.com/releases/2017/05/170501131759.htm"]City of Hope material[/link]
[link url="http://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-017-0840-7"]Breast Cancer Research abstract[/link]