Nonsteroidal anti-inflammatory drug use and breast cancer risk

Findings from previous epidemiological studies are inconclusive, though the y suggest nonsteroidal antiinflammatory drug (NSAID) use is associated with a reduction in breast cancer risk. In addition, animal studies report that NSAIDs inhibit mammary tumor development. The association between NSAID us e and breast cancer risk was evaluated using a case-control study design. C ases were a random sample of women diagnosed with a first primary cancer of the breast, aged 25-74 years, identified through the Ontario Cancer Regist ry, and diagnosed between July 1996 and September 1998. Controls were an ag e-matched random sample of the female population of Ontario. Cases (n = 313 3) and controls (n = 3062) completed a mailed questionnaire with informatio n on their past use of NSAID and other medications, as well as many risk fa ctors thought to be associated with breast cancer. Multivariate logistic re gression analysis was used to obtain adjusted odds ratio (OR) estimates. Us e of any NSAID medication (daily use for greater than or equal to2 months) was found to be associated with a significant 24% reduction in breast cance r risk (OR = 0.76; 95% confidence interval: 0.66, 0.88). The reduced risk w as strongest for use lasting >8 years, compared with nonusers (OR = 0.68; 9 5% confidence interval: 0.54, 0.86). No marked trends were observed for tim e since first use or last use or age at first use. Our results suggest a re duction in breast cancer risk associated with any regular NSAID use. NSAID use is a modifiable factor, and any protective effect attributed to its use could be of great public health importance.