Risk of ischemic stroke with tamoxifen treatment for breast cancer: A meta-analysis

Objective: To assess the overall risk of stroke, specifically ischemic stroke, associated with tamoxifen use by performing a meta-analysis of data reported in breast cancer trials. Background: Tamoxifen increases the risk of venous thromboembolism in women with breast cancer, but its relationship to stroke risk is uncertain. Methods: A systematic review of randomized controlled trials of tamoxifen for breast cancer management and prevention published since 1980 was performed using MEDLINE. The summary odds ratio (OR) and 95% CI were calculated using the Mantel-Haenszel method, followed by a statistical test for heterogeneity. Results: Nine trials met the inclusion criteria, and six trials specified ischemic stroke outcomes. The Mantel-Haenszel summary OR was 1.82 (95% CI, 1.41 to 2.36) for ischemic stroke and 1.40 (1.14 to 1.72) for any stroke. The χ² heterogeneity test was 6.0 (p > 0.1) for ischemic stroke and 16.1 (p < 0.05) for any stroke. The random-effects summary OR of Der Simonian and Laird for any stroke was 1.29 (0.92 to 1.81). During a mean follow-up period of 4.9 years, the frequency of ischemic stroke was 0.71% with tamoxifen vs 0.39% for controls (absolute increased risk, 0.32%; number needed to harm [NNH], 313). Conclusions: Women with breast cancer who were treated with tamoxifen had an 82% increased risk of ischemic stroke and a 29% increased risk of any stroke, but the absolute risk is small. Further studies assessing prespecified cerebrovascular outcomes are ongoing and will further clarify the risk of stroke associated with tamoxifen use.