Incidence, predictors, and recovery of acute chemotherapy-related left ventricular dysfunction in breast cancer patients: A prospective US cohort study.

e12528 Background: Advancements in breast cancer therapies, including anthracycline-based regimens and targeted agents like trastuzumab, have improved survival but heightened risks of cardiotoxicity, particularly chemotherapy-related cardiac dysfunction (CTRCD). This study assesses the incidence, predictors, and recovery patterns of acute left ventricular dysfunction (LVD) in US breast cancer patients receiving contemporary chemotherapy. Methods: In this prospective observational study, 97 adults with newly diagnosed breast cancer underwent serial echocardiographic assessment, including left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS), before, during, and after chemotherapy. CTRCD was defined as a > 10% decline in LVEF, LVEF < 50%, or a > 15% relative reduction in GLS. Clinical, oncologic, and treatment-related variables were analyzed. Results: Approximately one in eight patients developed CTRCD during chemotherapy. Nearly half of cases were detected by mid-treatment, highlighting the value of early surveillance. Left-sided breast involvement and pre-existing hypertension were more frequently observed among affected patients. Estrogen receptor–positive disease demonstrated a higher association with CTRCD. Trastuzumab-containing regimens showed a disproportionately higher occurrence of left ventricular dysfunction compared with other therapies. Importantly, following chemotherapy modification and guideline-directed heart failure therapy, over 75% of patients demonstrated improvement in left ventricular function within three months. Conclusions: CTRCD occurs early during breast cancer therapy but is frequently reversible with prompt detection and intervention. Focused cardiac monitoring, particularly in patients receiving trastuzumab or with left-sided disease, may enable early recovery and continuation of oncologic therapy.