Parity modifies the relationship between NSAIDs and ovarian cancer Free

B111

There is biologic evidence that increased inflammation might be associated with the development of ovarian cancer. The regular use of non-steroidal anti-inflammatory drugs (NSAIDs) could reduce the risk of ovarian cancer. We examined the association of NSAIDs and ovarian cancer, and whether the association was modified by parity, an important risk factor for this disease. In a population-based case-control study conducted in Wisconsin and Massachusetts during 1998-2001, we enrolled ovarian cancer cases (n=487) aged 20-74 years identified through the state-wide cancer registry, and similarly-aged controls (n=2653) randomly selected from lists of licensed drivers and Medicare beneficiaries. Information on NSAIDs, including use of aspirin and other NSAIDs, and established ovarian cancer risk factors was obtained via telephone interview. Odds ratios (OR) and 95% confidence interval were calculated using multivariate logistic regression, including terms for age, year of interview, state, body mass index (BMI), parity, hysterectomy status, oral contraceptive use, and menopausal status. Overall there was a 26% reduction in ovarian cancer risk among women who had ever used any type of NSAID (95% CI 0.59-0.92) compared to never users. Current users, though not former users, had a significant reduction in risk relative to never users. There were no linear trends associated with duration of use. An inverse association was also evident for current exclusive use of aspirin or other NSAIDs. Stratifying by parity, we observed a stronger inverse association with ever use of any NSAID in nulliparous (OR=0.47, 95% CI 0.27-0.82) than parous women (OR=0.81, 95% CI 0.64-1.04) (p-heterogeneity=0.05). Results of this study suggest that regular use of NSAIDs reduces the risk of ovarian cancer, particularly in nulliparous women.