Risk of the most serious cardiovascular events, cardiac ischemia and stroke, were not increased in breast cancer patients taking aromatase inhibitors compared with tamoxifen users. However, risk for other cardiovascular disease, including dysrhythmia, valvular dysfunction, and pericarditis, was increased in women who used aromatase inhibitors only or sequentially after tamoxifen compared with tamoxifen and with nonhormone users.1

For women who used only aromatase inhibitors or who used the drugs after tamoxifen, the risk of the less serious cardiovascular events was 26% to 29% higher than for those who used only tamoxifen. These events include abnormal heart beat and pericarditis.

Cardiovascular disease is a leading cause of death in older breast cancer survivors. Although the risk of cancer recurrence is reduced more by aromatase inhibitors than by tamoxifen, previous studies have provided inconclusive or mixed results on the potential cardiovascular risk associated with aromatase inhibitors.

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“Our study is a comprehensive assessment of the impact aromatase inhibitors have on cardiovascular risk and provides reassurance that the hormone therapy to reduce breast cancer recurrence does not increase risk of the most fatal cardiovascular events,” noted Reina Haque, PhD, MPH, research scientist, Kaiser Permanente Southern California Department of Research & Evaluation in Pasadena, California.

“A particular strength of our study is that we accounted for women’s other potential cardiovascular risk factors as well as medication used to treat high blood pressure and high cholesterol.”

The study included a cohort of 13 273 postmenopausal breast cancer survivors with either estrogen or progesterone receptor-positive breast cancer diagnosed from 1991-2010. The patients were followed through 2011, or a maximum of 21 years. This represents 72 886 person-years. The study participants were divided into 4 groups based on the drugs they received: 31.7% were treated only with tamoxifen; 28.6% only with aromatase inhibitors; 20.2% used both; and 19.4% did not use any of these drugs. During the follow-up period, 3711 cardiovascular events occurred.


1. Haque R, Shi J, Schottinger JE, et al. Cardiovascular disease after aromatase inhibitor use [published online ahead of print April 21 2016]. JAMA Oncology. doi:10.1001/jamaoncol.2016.0429.