A new report based on 4,164 women in the Nurses' Health Study indicates that aspirin use is associated with reduced risk of breast cancer metastasis and death. Results of previous studies indicate that aspirin might inhibit breast cancer metastasis. Study participants were diagnosed with breast cancer (stages I, II, or III) during the period 1976 to 2002 and followed either until June 2006 or death (if death occurred by June 2006). Aspirin use was categorized according to no use, 1 day, 2 to 5 days, or 6 to 7 days per week, and the level of use for each woman was first determined at least 12 months after diagnosis and updated thereafter. During the follow-up period, 400 hundred of the women experienced metastasis and 341 died from breast cancer.

Aspirin use was found to be associated with reduced risks of breast cancer recurrence and death. The study found an approximate 50% reduction in risk of metastasis for those taking aspirin at least two days per week. The findings did not vary significantly when analyzed based on breast cancer stage, menopausal status, body mass index (BMI), or estrogen receptor status. Women who took other non-steroidal inflammatory drugs (NSAIDs) at least 6 days per week also were found to have almost a 50% reduction in risk of breast cancer death (no such benefit was found for acetaminophen use). The authors conclude that among women living at least one year after a breast cancer diagnosis, aspirin use was associated with reduced risks of distant recurrence and death from breast cancer.

Previous studies show interaction between aspirin and cancer is complex

The fact that the effect of taking aspirin did not vary based on menopausal status, body mass index, or estrogen receptor status suggests that aspirin does not influence breast cancer progresssion through hormonal pathways. Therefore, aspirin's impact on inflammation is the most likely mechanism of action. This would help explain why aspirin might be less effective in preventing breast cancer than in preventing its spread. We summarize some previous study findings below:

  • A recent 2010 study reported that aspirin (but not other NSAID) use was associated with lower risk of ovarian cancer but not of endometrial cancer among participants in the Iowa Women's Health Study
  • A study examining the associations between consuming meat, aspirin use and breast cancer found that breast cancer risk was elevated among women who ate meat, especially flame broiled meat, and that aspirin use reduced the meat consumption-related increase in risk
  • A review of the effects of aspirin and NSAIDs on breast and ovarian cancers reported that they appear to inhibit the carcinogenesis of breast and ovarian cancers. However, not all the studies reviewed were in agreement. The anti-tumor effects of aspirin and other NSAIDs were thought to arise primarily from an inhibition of cyclooxygenase-2 (COX-2)
  • A large U.S. prospective study that included 77,413 women found no reduced risk of breast cancer associated with aspirin or other NSAID use
  • A prospective study of the association between NSAID use and risk of breast cancer in the 114,460 women in the California Teachers Study cohort found that long-term daily use of NSAIDs was not associated with breast cancer risk overall. However, long-term daily aspirin use was found to be associated with an increased risk of ER-/PR- breast cancer. In addition, ibuprofen (Advil, Motrin) use was associated with increased risk of breast cancer.

What to do with the information breast cancer survivors

This is the first study to find clear associations between aspirin use and survival after breast cancer treatment and the findings should be confirmed. Long-term aspirin use will produce undesirable side effects in some women. Also, note that the results for aspirin may not apply to other NSAIDs. Assuming that aspirin helps reduce the risk of recurrence by reducing inflammation, we would recommend adopting a lifestyle and diet designed to minimize inflammation.

Lifestyle strategies to reduce inflammation include performing moderate regular exercise, reducing stress, and getting enough sleep. Processed foods, high glycemic index foods such as white bread, high omega-6 oils such as corn oil, and high-fat dairy products such as butter all increase inflammation. On the other hand most fruits and vegatables, high omega-3 food such as wild salmon and walnuts, and healthy fats such as olive oil all reduce inflammation. We recommend selecting foods from our list of recommended foods and reducing exposure to the foods on our foods to avoid list.

Note that aspirin can interfere with chemotherapy and should not be used during such treatment.