Abstract
BackgroundRegular 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.MethodsIn 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.ResultsDeveloping 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.ConclusionOur 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.
Highlights
Regular users of aspirin may have reduced risk of breast cancer
To add to the evidence on low-dose aspirin, other non-steroidal anti-inflammatory medications (NSAIDs) including regular dose aspirin, and the risk of hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2)-defined breast cancer subtypes, we looked to our long-term prospective cohort of California public school professionals who were asked in 2005–2006 about current use of painrelieving medications, including low-dose aspirin, regular-dose aspirin, ibuprofen, and other NSAIDs
With over 7 years of follow up of incident breast cancer (n = 1457) including crucial detail on tumor HER2 status since submission of the 2005–2006 questionnaire, we evaluated whether risk of breast cancer varied by recent use of NSAIDs, and explored whether any associations between NSAIDs and risk of breast cancer were modified by HER2-defined breast cancer subtypes or overweight status
Summary
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. In a more recent assessment of 32 studies the authors concluded that aspirin use was not associated with risk of breast cancer, a statistically significant reduction in the risk of hormone receptor (HR)-positive subtypes was noted [5]. Both of these meta-analyses detected substantial heterogeneity of results among studies [4, 5]. Heterogeneity in the results for aspirin may be explained by previous studies not distinguishing between low-dose or daily aspirin use, which are common patterns of NSAID use that may be misclassified in broader categorizations, such as all doses of aspirin combined or use of three or more tablets per week
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