Longer-term aspirin use and subsequent ovarian cancer risk in the Ovarian Cancer Cohort Consortium.

BACKGROUND: Observational studies have reported lower ovarian cancer risk among individuals taking aspirin frequently (i.e. daily/near daily). However, most studies relied on a single assessment of aspirin use, which may have led to misclassification and precluded the examination of patterns of use over time. We examined the association between aspirin use, assessed at multiple time points, and ovarian cancer risk. METHODS: Data were pooled from 10 prospective cohort studies from the Ovarian Cancer Cohort Consortium (n = 675 901 participants; 5528 cases; median follow-up = 13 years). Frequent aspirin use was self-reported via repeat questionnaires. We examined multiple time-updated, lagged aspirin-exposure metrics and risk of ovarian cancer by using pooled logistic regression adjusted for time-updated confounders. RESULTS: While ever frequent aspirin use was not associated with ovarian cancer [odds ratio (OR) 0.97; 95% confidence interval (CI): 0.91-1.03], individuals who reported long-term use experienced a 14% reduction in ovarian cancer risk (>6 years; OR 0.86; 95% CI: 0.77-0.97). This risk reduction was evident among individuals with at least three ovarian cancer risk factors (OR 0.65; 95% CI: 0.50-0.85) but not among individuals with fewer than three ovarian cancer risk factors (OR 0.94; 95% CI: 0.82-1.08), P-interaction = .02). Reduced ovarian cancer risks were also observed for low-dose aspirin use (OR 0.90; 95% CI: 0.80-1.01 for ever low-dose use; OR 0.75; 95% CI: 0.56-0.99 for long-term low-dose use) but not ever regular-dose use (OR 1.09; 95% CI: 0.94-1.27). CONCLUSION: Long-term use of aspirin, and particularly low-dose aspirin, is associated with lower ovarian cancer risk, especially among individuals with other established risk factors for ovarian cancer. Research should continue to explore the potential role of long-term, low-dose aspirin use for ovarian cancer primary prevention.