Cardiac function surveillance practices and outcomes in patients with HER2-positive breast cancer treated with trastuzumab: a retrospective cohort study across a safety-net and tertiary care setting

Anti-HER2 receptor monoclonal antibodies like trastuzumab are the mainstay of treatment in HER2-positive breast cancer but can result in cancer therapy-related cardiac dysfunction (CTRCD). Guidelines recommend cardiac surveillance prior to anti-HER2 therapy initiation, every 3 months during therapy, and within 1 year after therapy completion. Resource limitations in safety-net settings without cardio-oncology programs may impact cardiac surveillance and treatment patterns and contribute to disparities in cardiovascular health among patients with cancer. We aimed to characterize and compare patterns of cardiac surveillance and short-term cardiovascular outcomes among patients with breast cancer receiving trastuzumab in a safety-net versus a tertiary care system. A retrospective cohort study was conducted on women diagnosed with stage I-III HER2-positive breast cancer between 2018 and 2020 in a safety-net and a tertiary care system. Clinical data from transthoracic echocardiograms, multigated acquisition scans, and cardiac magnetic resonance imaging one year out from trastuzumab initiation were collected. CTRCD was defined by decrements in left ventricular ejection fraction, global longitudinal strain changes, and symptoms of heart failure. Demographics and referral patterns were also assessed. A total of 235 patients were included (93 safety-net, 142 tertiary care). The safety-net population was 23% Black, 60% Hispanic, and 69% uninsured, while the tertiary care population was 64% White and 3.5% uninsured (p < 0.001). Baseline cardiac surveillance was obtained in 84% of safety-net patients and 89% of tertiary care patients, with mean surveillance interval of approximately 3 months. Only 54% of patients at each site obtained cardiac surveillance post-trastuzumab. CTRCD occurred in 12% of patients in the safety-net system and 19% in the tertiary care system, with most cases being asymptomatic (p = 0.143). High-risk patients were more likely to be referred to cardiology/cardio-oncology in the tertiary care system compared to the safety-net system (67% vs. 6.7%, p < 0.001). While our data shows similar frequency of cardiac surveillance based on left ventricular ejection fraction at our safety-net and tertiary care center, the utilization of various imaging modalities and cardiology/cardio-oncology services were significantly different between the two institutions. These differences may result in underdiagnosis of CTRCD in vulnerable populations and contribute to inferior long-term cardiovascular outcomes.