Although heart failure is a relatively common complication in older women undergoing treatment for breast cancer, adjuvant trastuzumab (Herceptin) therapy appears to raise the risk to an even greater degree.

“We observed an even higher risk of heart failure or cardiomyopathy after trastuzumab therapy than those in past clinical trials,” noted Jersey Chen, MD, MPH, lead author of the study demonstrating this outcome, in a statement from Yale University in New Haven, Connecticut. Chen is assistant professor of cardiology at Yale University School of Medicine and a member of the Yale Cancer Outcomes, Public Policy, and Effectiveness Research Center (COPPER).

As Chen and colleagues wrote in Journal of the American College of Cardiology, trastuzumab and other newer biologic therapies for breast cancer have been reported to increase heart failure and cardiomyopathy in clinical trials, particularly when this monoclonal antibody is administered in combination with anthracycline chemotherapy. However, elderly patients have been underrepresented in clinical trials of trastuzumab.

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Chen’s group pointed out that 40.8% of women diagnosed with breast cancer in the United States are age 65 years and older, and risk for cardiovascular events increases with age. Therefore, the researchers contended, gaining a better understanding of the risk of cardiotoxicity associated with trastuzumab and chemotherapy in older adults is crucial.

The investigators evaluated Surveillance, Epidemiology, and End Results (SEER)–Medicare data from 45,537 women aged 67 to 94 years (mean age 76.2 years) with early-stage breast cancer. They found that the adjusted 3-year incidence rates for heart failure or cardiomyopathy were higher for women receiving trastuzumab (32.1 per 100 patients) and anthracycline plus trastuzumab (41.9 per 100 patients) compared with no adjuvant therapy (18.1 per 100 patients).

Adding trastuzumab to anthracycline therapy added 12.1, 17.9, and 21.7 heart failure or cardiomyopathy events per 100 patients over 1, 2, and 3 years of follow-up, respectively.

“Further study is needed to fully understand the benefits and risks of trastuzumab. . .in the real-world population,” acknowledged Cary P. Gross, MD, senior author of the study and director of the COPPER Center, in the Yale statement.