Daily intake of aspirin reduces the risk of developing estrogen receptor (ER) – positive breast cancer, according to a study published in the recent issue of an open access journal, Breast Cancer Research.

In order to study the association between NSAIDs (nonsteroidal anti-inflammatory drugs) usage and the incidence of breast cancer, Gretchen L Gierach, lead author of the study, and coworkers, evaluated questionnaires (1996-1997) answered by 127,383 women, aged 51 to 72 years (with no history of cancer), enrolled in the National Institutes of Health-AARP (American Association of Retired Persons) Diet and Health Study. Analysis using multivariate Cox proportional hazards regression models showed no significant association between the use of NSAIDs and total breast cancer risk. However, further research on the subtypes of breast cancer and their association with various NSAIDs has shown that the daily intake of aspirin, unlike other NSAIDs, reduces the incidence of developing ER-positive breast cancer.

Aspirin and other NSAIDs suppress estrogen biosynthesis, a crucial pathogenic factor in the development of ER-positive breast cancer, by inhibiting cyclooxygenase-2 activity, which in turn reduces the production of prostaglandin (essential for stimulating estrogen biosynthesis). Terry and colleagues (Journal of the American Medical Association, 2004) conducted a population-based case-control study (1996-1997) involving 1,442 breast cancer cases and 1,420 controls, on Long Island, New York, to investigate the link between the use of aspirin, and other NSAIDs (ibuprofen, acetaminophen) and breast cancer risk (especially in ER-positive cases). Regular intake of acetaminophen and ibuprofen was not considerably associated with the incidence of breast cancer; however, the regular use of aspirin (≥7 tablets per week) exhibited a positive effect against hormone receptor-positive breast cancer. Based on the study results, the authors suggested that the regular intake of a class of NSAIDs that inhibit estrogen biosynthesis, may serve as an effective chemopreventive agent for hormone-receptor positive breast cancer.

Earlier studies have suggested that analgesics could also reduce the risk of other types of cancer like ovarian cancer. With the purpose of assessing the effects of analgesics in reducing the risk of epithelial ovarian cancer, Schildkraut and coworkers (Epidemiology, 2006) carried out a population-based, case control study involving 586 positive cases and 627 matched controls, in North Carolina. Using logistic regression analysis, researchers found that the regular use of NSAIDs, including aspirin within 5 years of diagnosis, was inversely correlated to the risk of developing the cancer.

Vishwanathan and colleagues (Cancer Research, 2008) carried out a prospective cohort study to investigate the association between the usage of aspirin, other NSAIDs such as acetaminophen, and endometrial adenocarcinoma. Calculation of multivariate relative risks (MV RR) adjusted for body mass index (BMI), postmenopausal hormone (PMH) use, and other endometrial cancer risk factors, revealed that the duration and dosage of aspirin was not associated with the overall endometrial cancer risk. However, endometrial cancer risk was considerably reduced among current aspirin users, who were either obese or in postmenopausal women (never used postmenopausal hormone).

Breast cancer, the most frequently diagnosed cancer, is the second leading cause of death among women in the US. The National Cancer Institute (NCI) estimates approximately 182,460 new breast cancer cases and deaths in 40,480 US women, in 2008. Aspirin, a commonly used over-the-counter medication, with analgesic, anti-inflammatory, anti-clotting, and antipyretic properties is now identified to have a positive chemoprotective effect in reducing the risk of estrogen receptor positive breast cancer, a hormone dependent breast cancer. Although the above studies project the protective benefits of aspirin against breast cancer, further research is required to evaluate the relationship between NSAIDs type and breast cancer subtype.

References

1. Gierach GL, Lacey JV Jr, Schatzkin A, et al. Nonsteroidal anti-inflammatory drugs and breast cancer risk in the National Institutes of Health-AARP Diet and Health Study. Breast Cancer Res. 2008 Apr 30;10(2):R38.

2. Terry MB, Gammon MD, Zhang FF, et al. Association of frequency and duration of aspirin use and hormone receptor status with breast cancer risk. JAMA. 2004 May 26;291(20):2433-40.

3. Schildkraut JM, Moorman PG, Halabi S, Calingaert B, Marks JR, Berchuck A. Analgesic drug use and risk of ovarian cancer. Epidemiology. 2006 Jan;17(1):104-7.

4. Viswanathan AN, Feskanich D, Schernhammer ES, Hankinson SE. Aspirin, NSAID, and acetaminophen use and the risk of endometrial cancer. Cancer Res. 2008 Apr 1;68(7):2507-2513.