Association between tamoxifen use and acute myocardial infarction in women with breast cancer

The relationship between tamoxifen use and acute myocardial infarction in women with breast cancer remains uncertain. The goal of the study was to assess whether tamoxifen use could be associated with acute myocardial infarction in women with breast cancer in Taiwan. A population-based case–control study was conducted to analyze the database of the Taiwan National Health Insurance Program. Totally, 489 women with breast cancer aged 20 to 84 years having the first episode of acute myocardial infarction from 2000 to 2011 were found as the cases. In addition, 1718 women with breast cancer aged 20 to 84 years without any type of ischemic heart disease were selected as the matched controls. Ever use of tamoxifen was classified as the studied women who had at least a prescription for tamoxifen before the index date. Never use of tamoxifen was classified as the studied women who never had a prescription for tamoxifen before the index date. We used the multivariable logistic regression model to estimate the odds ratio (OR) and 95% confidence interval (CI) for acute myocardial infarction associated with tamoxifen use. In a multivariable-adjusted analysis, women with acute myocardial infarction were 1.71 times more likely to be exposed to tamoxifen than those women without acute myocardial infarction (adjusted OR 1.71, 95% CI 1.38–2.13). The odds of tamoxifen use are 1.71 times higher in women with acute myocardial infarction versus those women without acute myocardial infarction in Taiwan.