Low Dose Aspirin and Breast Cancer Prevention – Results from the CTS Cohort

Purpose

Low-dose (81 mg) aspirin is recommended by USPSTF to reduce cardiovascular disease and colorectal cancer. As previous studies were inconclusive on the role of aspirin in the prevention of breast cancer, the aim of this study by Clarke et al. (Breast Cancer Res, 2017) was to determine whether hormone receptor subtypes (HR) and Her-2/neu receptor (HER2) status may be responsible for the variability in previous studies.

Methods

Observational Longitudinal Cohort: This study assessed data collected over several years from the California Teachers Study cohort. The cohort began in 1995-1996 and initially included 133,479 women, followed with baseline and ongoing annual questionnaires on family history and other cancer risk factors. The 2005-2006 questionnaire incorporated use of aspirin and other pain medications. In addition, the above data was linked to the California Cancer Registry and Office of Statewide Health Planning and Development which provides information on hospital services.

Results

Key findings include:

• Overall, current use of at least three tablets a week of any NSAID was not associated with breast cancer
• 3 or more tablets of low-dose aspirin per week was associated with a reduction in breast cancer, with a hazard ratio of 0.84 (95% CI 0.72-0.98)
  • The reduction in breast cancer was only observed in the case of positive HR/ HER2 negative status, with a hazard ratio of 0.80 (95% CI 0.66-0.96)
• Timing and Frequency: 3 – 6 tablets of low-dose aspirin per week was further associated with breast cancer reduction compared to women not taking any NSAIDs during the past 3 years, with a hazard ratio of 0.72 (95% CI 0.54-0.96)
  • Similarly, this inverse association held for the HR positive/ HER negative status subtypes
• Of note, the aspirin effect was seen with low-dose and not regular dose aspirin (325 mg)

Summary

• This study demonstrates a 20% risk reduction for HR positive/Her2-negative breast cancer when low dose aspirin was used at least 3 times/week
• Regular use, rather than sporadic use for pain may be a key factor in breast cancer reduction
• Strengths of study:
  • Complete and accurate prospective data collection
• Limitations of study:
  • Other possible confounders that were not obtained in the questionnaires (e.g. perhaps regular aspirin takers exercise more)
  • Observational and not interventional – questionnaires are ‘snapshots’ in time
  • Population used for this study may not mirror general population (e.g. educational status)

Learn More – Primary Sources

Regular and low-dose aspirin, other non-steroidal anti-inflammatory medications and prospective risk of HER2-defined breast cancer: the California Teachers Study

Related ObG Topics:

Professional Recommendations for Use of Pharmacologic Interventions to Reduce Breast Cancer Risk

Atypical Hyperplasia of the Breast: Follow-up and Management

Office Evaluation of Breast Disorders