Our results provide further evidence that tamoxifen reduces the risk of myocardial infarction. Thromboembolic events should be carefully monitored in trials of tamoxifen, particularly those of prophylactic treatment, in which tamoxifen is given to healthy women.

Objective-To investigate the incidence of fatal myocardial infarction in women in the two randomised arms of the Scottish adjuvant tamoxifen trial.Design-Retrospective review of hospital notes to determine with the greatest possible certainty women who had died of an acute myocardial infarction.Setting-Scottish Cancer Trials Office, the University of Edinburgh.Patients-1070 postmenopausal women with operable breast cancer who were randomised to receive either adjuvant tamoxifen for five years or until relapse (539 patients) or tamoxifen for at least six weeks on the confirmation of first recurrence (531 patients).Main outcome measures -Incidence of fatal myocardial infarction in women with no known or suspected systemic cancer.Results-Of the 200 women who died in the adjuvant tamoxifen arm of the trial, 44 were free of cancer at death and 10 of these died of myocardial infarction. In the observation arm 251 women died, of whom 61 showed no evidence of systemic cancer and 25 had a fatal myocardial infarction. The incidence of fatal myocardial infarction in the two groups was significantly different (X2=6-88, p=00087).Conclusion-Tamoxifen given for at least five years as adjuvant therapy for breast cancer seems to have a cardioprotective oestrogen-like effect in postmenopausal women.

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