Tamoxifen-treated breast carcinoma patients and the risk of acute myocardial infarction and newly-diagnosed angina.

BACKGROUND: It is known that tamoxifen therapy favorably affects blood cholesterol levels and other cardiovascular disease risk factors; however, to our knowledge, few studies to date have reported a lower risk of heart disease for breast carcinoma patients who are treated with tamoxifen.
METHODS: A nested, matched, case-control study design was used with data from the General Practice Research Database to examine whether patients with breast carcinoma who had been treated with tamoxifen were at reduced risk of having a first acute myocardial infarction (MI) or of developing angina compared with unexposed women. All women between age 30 years and age 85 years who had been diagnosed with breast carcinoma and treated with tamoxifen, or who had been diagnosed with carcinoma of the bladder or colorectum, or nonmelanoma skin cancer between January 1991 and December 1999 were identified. From this population, all women were identified who had newly diagnosed acute MI or angina that occurred at least 1 year after their cancer diagnosis. Four female control participants were matched to each case based on age (+/- 1 year), date of MI or angina diagnosis (corresponding date for matched controls), and date of cancer diagnosis (+/- 6 months). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were generated using conditional logistic regression, controlling for the matching factors, and adjusting for important risk factors, including body mass index, use of hormone replacement therapy, smoking status, and treated hypertension.
RESULTS: Current users of tamoxifen had a reduced rate ratio of acute MI or angina (adjusted OR, 0.4; 95% CI, 0.2-0.7) compared with nonusers. The effect persisted with increasing cumulative dose and length of use.
CONCLUSIONS: The treatment of breast carcinoma with tamoxifen was found to reduce a woman's risk of acute MI or angina during the 5 years of recommended therapy.