An analysis of data from the Nurse’s Health Study, a large, ongoing prospective observational study, shows that women who have completed treatment for early-stage breast cancer and who take aspirin have a nearly 50 percent reduced risk of breast cancer death and a similar reduction in the risk of metastasis.
“This is the first study to find that aspirin can significantly reduce the risk of cancer spread and death for women who have been treated for early-stage breast cancer, " said Michelle Holmes, MD, DrPH, associate professor of medicine and epidemiology at Harvard Medical School & Harvard School of Public Health and the study's lead author. “If these findings are confirmed in other clinical trials, taking aspirin may become another simple, low-cost and relatively safe tool to help women with breast cancer live longer, healthier lives."
Investigators report it is not yet clear how aspirin affects cancer cells, but they speculate it decreases the risk of cancer metastasis by reducing inflammation, which is closely associated with cancer development. Prior studies have also suggested that aspirin inhibits cancer spread: one study found that people with colon cancer who took aspirin lived longer than those who did not, and laboratory studies have also shown that aspirin inhibited the growth and invasiveness of breast cancer cells.
In this analysis, researchers evaluated data from the Nurses' Health Study, which included 4,164 female nurses in the United States (ages 30 to 55 in 1976) who were diagnosed with stage I, II, or III breast cancer between 1976 and 2002 and were followed through June 2006. They examined patients’ use of aspirin for one or more years after a breast cancer diagnosis (when patients would have completed treatment such as surgery, radiation therapy, and/or chemotherapy) and the frequency of metastasis and breast cancer death. (The authors emphasized that patients undergoing active treatment should not take aspirin due to potential interactions that can increase certain side effects.)
A total of 400 women experienced metastasis, and 341 of these died of breast cancer. Women who took aspirin two to five days per week had a 60 percent reduced risk of metastasis and a 71 percent lower risk of breast cancer death. Those who took aspirin six or seven days a week had a 43 percent reduced risk of metastasis and a 64 percent lower risk of breast cancer death. The risk of breast cancer metastasis and mortality did not differ between women who did not take aspirin and those who took aspirin once a week.
Researchers also found that women who took non-aspirin non-steroidal inflammatory drugs (NSAIDs) six or seven days a week also had a reduced risk of breast cancer death (a 48 percent reduction), but women who took NSAIDS less frequently and those who used acetaminophen did not experience such a benefit.
While the investigators did not collect data on aspirin dose, they noted that women who took aspirin regularly most likely took it for heart disease prevention; the typical dose for that purpose is 81 mg/day.
Lori Pierce, MD, Member, ASCO’s Cancer Communications Committee
“Several studies have suggested that aspirin may have beneficial effects against cancer because of its anti-inflammatory effects. But aspirin can cause stomach bleeding and is not for everyone. These are promising findings, and if they are confirmed in additional clinical trials, physicians may be able to regularly recommend aspirin to their breast cancer patients to reduce risk of cancer spread and mortality.”