Association Between Body Mass Index and Cardiac Dysfunction During Human Epidermal Growth Factor Receptor 2 Inhibitor Therapy for Breast Cancer.

BACKGROUND: The administration of human epidermal growth factor receptor 2 inhibitors (HER2i) has improved the survival of patients with breast cancer; however, cancer therapy-related cardiac dysfunction (CTRCD) has been reported as an adverse effect. In this study we evaluated the incidence of CTRCD associated with HER2i treatment and explored risk factors for a decrease in left ventricular function. METHODS AND RESULTS: This retrospective study included 94 female patients with breast cancer treated at Kanazawa Medical University Hospital from January 1, 2017, to August 31, 2023. Clinical, hematologic and echocardiographic data were collected. The median pretreatment body mass index (BMI; 22.3 kg/m2) was used to divide patients into low- and high-BMI groups. Changes in red cell distribution width (RDW), left ventricular ejection fraction (LVEF), and global longitudinal strain (GLS) were evaluated. A total of 32 patients showed a decrease in LVEF 6 months after treatment initiation, and 2 had LVEF <50% with a ≥10% decrease. The rate of LVEF decrease was significantly greater in the low-BMI group than in the high-BMI group (-5.1% vs. -0.4%, P=0.023). No association was observed between RDW or GLS and LVEF. CONCLUSIONS: Low BMI was associated with a greater risk of cardiotoxicity during HER2i treatment. Careful cardiac monitoring is particularly recommended for patients with low BMI.