Choosing Safe Endocrine Treatment in Breast Cancer Remains Challenging

A new study by researchers at Kaiser Permanente and University of California at Los Angeles has concluded that breast cancer patients treated with aromatase inhibitors (AIs) as adjuvant endocrine therapy were at equal risk of serious cardiovascular disease (CVD) events, as compared with those treated with tamoxifen.

Researchers conducted a retrospective analysis of more than 13,000 postmenopausal women with breast cancer who were diagnosed between January 1, 1991, and December 31, 2010. The women were followed up till December 31, 2011. The diagnosis was for hormone receptor—positive breast cancer without CVD complications. The women received adjuvant endocrine therapy of tamoxifen citrate alone, AI alone, or neither, and were grouped accordingly.

During the follow-up period, a total of 3711 CVD events were recorded. Of these, AI-only users has a similar risk of cardiac ischemia (myocardial infarction and angina) (adjusted hazard ratio [HR], 0.97; 95% CI, 0.78-1.22) and stroke (adjusted HR, 0.97; 95% CI, 0.70-1.33) when compared with those treated with tamoxifen alone. However, using AI alone (adjusted HR, 1.29; 95% CI, 1.11-1.50) or subsequent to tamoxifen (adjusted HR, 1.26; 95% CI, 1.09-1.45), increased the women’s risk of other CVDs (dysrhythmia, valvular dysfunction, and pericarditis).

“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,” said Reina Haque, PhD, MPH, research scientist, Kaiser Permanente Southern California Department of Research & Evaluation, in a statement. Haque is the lead author on the study, which has been published in JAMA Oncology. “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.”

Based on their findings, the authors believe that further studies to assess the risk of other CVD events are warranted.

Reference

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