NSAID use and breast cancer risk in the VITAL cohort.

OBJECTIVE: We prospectively evaluated the association between average 10-year use of NSAIDs and invasive breast cancer.
METHODS: Between 2000-2002, 35,323 postmenopausal women participating in the Vitamins And Lifestyle (VITAL) study provided detailed information regarding NSAID use, lifestyle and breast cancer risk factors. Using a Cox proportional hazards model, we analyzed associations between NSAID use and incident breast cancer (N = 482) ascertained through linkage to the SEER cancer registry.
RESULTS: Use of low-dose aspirin at 4+ days/week over ten years was associated with a decreased risk of breast cancer (HR 0.65, confidence interval [CI] 0.43-0.97) versus no use, as was moderate use of other types of NSAIDs (HR 0.78, CI 0.61-0.98) for 10-yr average use up to 3 days/week. However, more frequent use of NSAIDs other than low-dose aspirin was associated with an increased risk (HR 1.26, CI 0.96-1.65), particularly frequent use of regular or extra strength aspirin (HR 1.43, CI 1.02-2.00).
CONCLUSIONS: We did not find evidence of a global protective effect of NSAID use for the development of breast cancer. However, long-term moderate use (frequent use of low doses or moderate frequency of high doses) was associated with reduced risk, while frequent use of higher dose products was associated with increased risk.