Background. The effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on
the risk of breast cancer is unclear. We assessed the association in a hosp
ital-based case-control study.
Methods. The cases (n = 6558) were compared with cancer controls (n = 3296)
and noncancer controls admitted for trauma or acute infection (n = 2925).
Odds ratios were estimated using multivariate logistic regression models.
Results. For women who used NSAIDs regularly beginning at least 1 year befo
re admission, the odds ratios (OR) were 0.8 (95% CI 0.7, 1.0) with cancer c
ontrols and 0.7 (95% CI 0.6, 0.9) with noncancer controls. With noncancer c
ontrols, there was a statistically significant decreasing trend in the odds
ratios as duration of use increased, whereas with cancer controls there wa
s not. The reduction in risk for regular use was accounted for largely by a
reduced odds ratio for one study center (Boston), which contributed 9% of
the cases.
Conclusions. The data are compatible with a small reduction in risk, associ
ated with regular NSAID use. However, inconsistencies in the data detract f
rom a causal interpretation. (C) 1999 American Health Foundation and Academ
ic Press.