The association between adiposity and cardiac function in patients with early breast cancer receiving cardiotoxic therapies

Background Anthracyclines and HER2-directed therapies improve survival in early breast cancer but increase cardiovascular risk, which body mass index poorly characterizes. We evaluated longitudinal associations between pre-treatment CT-derived body composition and echocardiography-derived systolic and diastolic function in a prospective cohort of women with early breast cancer. Methods In a prospective cohort of women with stage I–III early breast cancer treated with anthracyclines and/or trastuzumab, skeletal muscle index (SMI), muscle density (SMD), and visceral and subcutaneous adipose tissue area and density (VAT, SAT, VATD, SATD) were quantified from pre-treatment CT or PET-CT at L3 using automated segmentation. Longitudinal changes in LVEF and E/e′ were analyzed using multivariable-adjusted GEE models. Time to incident systolic dysfunction (≥ 10% LVEF decline to < 50%) and diastolic dysfunction (E/e′ ≥ 14) were analyzed using Cox proportional hazards models. Results Across 177 participants (median age 50 years, 36.2% HER2-positive, 19.9% triple-negative), 145 (81.9%) received anthracycline-based therapy. Baseline body composition was not associated with longitudinal LVEF change. Higher baseline VAT (β 0.6, 95% CI 0.2–0.9; p = 0.001) and VAT/SAT ratio (β 0.5, 95% CI 0.2–0.7; p < 0.001) were associated with increased E/e′ over time, while higher VATD (β − 0.4, 95% CI − 0.6 to − 0.1; p = 0.002) was associated with decreased E/e′ during follow-up. No associations were observed for SAT or SATD. Conclusions Pre-treatment visceral adiposity is associated with worsening diastolic function during breast cancer therapy. CT-derived body composition may refine cardiotoxicity risk assessment beyond BMI.