Low-Dose Aspirin May Lower Ovarian Cancer Risk

Women who reported recent, regular use of low-dose aspirin (100 milligrams or less) had a 23% lower risk of developing ovarian cancer when compared with women who did not regularly take aspirin, according to new research led by Harvard T.H. Chan School of Public Health. The research team, which analyzed data from more than 200,000 women in the Nurses’ Health Studies, at Brigham and Women’s Hospital, say the results showed that the protective effects of aspirin only appear to be evident at low dose, not standard dose, while heavy, prolonged use of non-aspirin non-steroidal anti-inflammatory drugs (NSAIDs) may increase the risk of ovarian cancer.

“We’re not quite at the stage where we could make the recommendation that daily aspirin use lowers ovarian cancer risk,” says research lead Shelley Tworoger, Ph.D., associate center director for population science at Moffitt. “We need to do more research. But it is definitely something women should discuss with their physician.”

Reporting their results in JAMA Oncology, the authors write, “To our knowledge, this prospective cohort study is among the first to evaluate in detail the associations between type, timing, frequency, quantity, and duration of analgesic use with risk of ovarian cancer by using regularly updated exposure information.” Their paper is titled, “Association of analgesic use with risk of ovarian cancer in the Nurses’ Health Studies.”

Ovarian cancer is the fifth most common cause of cancer-related deaths among women in the U.S., and growing evidence suggests a role for inflammation in the development of the disease, the authors write. Previous case-control and prospective studies investigating whether regular use of anti-inflammatory drugs such as aspirin or nonaspirin NSAIDs might have an effect on ovarian cancer risk have been mixed. Moreover, the authors comment, “no prospective cohort studies have had adequate power and sufficiently detailed exposure to evaluate whether timing and patterns of analgesic use are associated with ovarian cancer risk.”

Dr. Tworoger and colleagues analyzed prospectively collected data on the timing, frequency, dose, and duration of analgesic use, from 93664 women enrolled in the Nurses’ Health Study (NHS) and from another 111834 women enrolled in the Nurses’ Health Study II (NHSII), to investigate any relationship between the use of aspirin, nonaspirin NSAID, and acetaminophen, with ovarian cancer.  Among the 205498 women in both cohorts, there were 1054 cases of ovarian cancer recorded over the course of the study period, which was up to 30 years.

The researchers’ analyses of the data found no association between total (low- and standard-dose) current aspirin use, years of aspirin use, or cumulative average tablets per week, with ovarian cancer risk. However, when low-dose and standard-dose aspirin use were evaluated separately over a five-year period, low-dose aspirin was associated with a 23% lower risk of ovarian cancer risk, compared with no use. “… there was no such association with current standard-dose aspirin use,” the authors write. Interestingly, current nonaspirin NSAID use was positively linked with risk of ovarian cancer, when compared with non-use, and there was a significant association between taking NSAIDs regularly for more 10 years, and ovarian cancer risk, “although this finding may reflect unmeasured confounding,” they acknowledge. There was also what the authors term “a suggestion of a positive association for acetaminophen use.”

Prior reports have suggested that aspirin may lower cancer risk by reducing inflammation. And while it is thought that the mechanism underpinning the dose-response link between aspirin and colon cancer is suppression of prostaglandin synthesis via inhibition of the cyclooxygenase 1 (COX-1) and COX-2 enzymes, the new results in ovarian cancer found no dose-response relationship, “suggesting that other mechanisms unique to low-dose aspirin (e.g., irreversible inhibition of platelet COX-1) may influence carcinogenesis by reducing platelet activation and recruitment.”

“These results support a lower risk of ovarian cancer among low-dose aspirin users, although the association between other nonsteroidal anti-inflammatory drugs and ovarian cancer may be more complex,” the authors conclude. “Further exploration is warranted to evaluate the mechanisms by which heavy use of aspirin, nonaspirin NSAIDs, and acetaminophen may contribute to the development of ovarian cancer and to replicate our findings.”