LVEF decline in relation to body composition among women treated for breast cancer: WF-97415.

10556 Background: Despite an improvement in survival from breast cancer (BC), many women experience cardiotoxicity. Left ventricular ejection fraction (LVEF) is reduced by an average of 9.7% in women receiving anthracyclines. Obesity and central adiposity at BC diagnosis may influence risk of LVEF decline. We sought to examine associations between body composition and LVEF decline in the UPBEAT (Understanding and Predicting Fatigue, Cardiovascular Decline, and Events After Breast Cancer: WF-97415) study, which was conducted in collaboration with NCI Community Oncology Research Program. Methods: The analytic cohort was comprised of 167 women treated for stage I-III BC with chemotherapy and/or radiation in the UPBEAT prospective study, in whom LVEF was obtained at baseline (pre-treatment) and 3 months. Linear regression was used to examine LVEF decline in relation to 1) waist circumference (WC) and body mass index (BMI) at baseline and 2) changes in WC and BMI during BC treatment. All models were adjusted for age and race. Results: In this cohort (mean [SD] age: 55.7 [10.8] yrs; in whom 75% were white; 19% were Black), the mean (SD) LVEF at baseline was 60.7 (6.7)% with a mean decline of 2.7 (7.2)% from baseline to 3-months. Both WC and BMI at BC diagnosis were associated with LVEF decline during follow-up (Table). For each additional inch in WC, EF decreased by 0.25% points at 3 months (P=0.024); for each additional kg/m 2 in BMI, EF decreased by 0.2% points at 3 months (P=0.007). Reduced BMI during treatment was associated with LVEF decline, whereas a change in WC was not. Each kg/m 2 reduction in BMI was associated with a 0.4% point decrease in LVEF (p=0.037). Anthracycline use was associated with a 1.89% point decline in LVEF at 3 months versus non-users (p=0.049). After additional adjustment for anthracycline use, baseline WC remained statistically significantly associated with LVEF decline to the same degree. Conclusions: These data show that central adiposity at BC diagnosis is associated with LVEF decline during treatment, even after controlling for anthracyclines. Loss of central adiposity was not associated with LVEF decline, whereas BMI loss during treatment was. This suggests that shifts in body composition during BC treatment, potentially via loss of muscle mass, are important to monitor in patients. Future work should examine how changes in body composition, particularly changes in skeletal muscle and adipose tissue depots, influence cardiac dysfunction in BC patients during treatment. Funding: 2UG1CA189824, R01CA199167, 2UG1CA189828. [Table: see text]