Question Are findings from case-control studies that report lower ovarian cancer risk among low-dose aspirin users reproducible in a large prospective study?
Findings This cohort study using data from the Nurses’ Health Study and Nurses’ Health Study II observed a 23% lower risk of ovarian cancer among current low-dose aspirin users compared with nonusers. However, current use of nonaspirin nonsteroidal anti-inflammatory drugs was associated with a 19% higher risk of ovarian cancer compared with nonuse, and positive trends were observed for duration and cumulative average tablets per week.
Meaning 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.
Importance Ovarian cancer is a highly fatal malignant neoplasm with few modifiable risk factors. Case-control studies have reported a modest reduced risk of ovarian cancer among women who frequently use aspirin or regularly use low-dose aspirin.
Objective To evaluate whether regular aspirin or nonaspirin nonsteroidal anti-inflammatory drug (NSAID) use and patterns of use are associated with lower ovarian cancer risk.
Design, Setting, and Participants This cohort study analyzed NSAID use and ovarian cancer diagnosis data from 2 prospective cohorts, 93 664 women in the Nurses’ Health Study (NHS), who were followed up from 1980 to 2014, and 111 834 in the Nurses’ Health Study II (NHSII), who were followed up from 1989 to 2015. Follow-up was completed on June 30, 2014, for the NHS and June 30, 2015, for NHSII. Data were analyzed from June 13, 2016, to September 18, 2017.
Exposures For each analgesic type (aspirin, low-dose aspirin, nonaspirin NSAIDs, and acetaminophen), timing, duration, frequency, and number of tablets used were evaluated; exposure information was updated every 2 to 4 years.
Main Outcomes and Measures Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% CIs for associations of aspirin, nonaspirin NSAIDs, and acetaminophen with risk of epithelial ovarian cancer. All statistical tests were 2-sided, with a significance level of .05.
Results In the NHS, the mean (SD) age at baseline (1980) was 45.9 (7.2) years, and 93% of participants identified as non-Hispanic white. In the NHSII, the mean age at baseline (1989) was 34.2 (4.7) years, and 92% identified as non-Hispanic white. Among the 205 498 women in both cohorts, there were 1054 cases of incident epithelial ovarian cancer. Significant associations between aspirin and ovarian cancer risk were not observed when current vs nonuse of any aspirin was evaluated regardless of dose (HR, 0.99; 95% CI, 0.83-1.19). However, when low-dose (≤100-mg) and standard-dose (325-mg) aspirin were evaluated separately, an inverse association for low-dose aspirin (HR, 0.77; 95% CI, 0.61-0.96), but no association for standard-dose aspirin (HR, 1.17; 95% CI, 0.92-1.49) was observed. Current use of nonaspirin NSAIDs was positively associated with risk of ovarian cancer compared with nonuse (HR, 1.19; 95% CI, 1.00-1.41), and significant positive trends for duration of use (P = .02 for trend) and cumulative average tablets per week (P = .03 for trend) were observed. There were no clear associations for the use of acetaminophen.
Conclusions and Relevance These results appear to be consistent with case-control studies that show a reduced risk of ovarian cancer among regular users of low-dose aspirin. An increased risk of ovarian cancer with long-term high-quantity use of other analgesics, particularly nonaspirin NSAIDs, was observed, although this finding requires confirmation.