Abstract
OBJECTIVES: This study determined the effects of doxorubicin and/or trastuzumab on diastolic function and the relationship between diastolic function and systolic dysfunction. BACKGROUND: Doxorubicin and trastuzumab can result in left ventricular ejection fraction (LVEF) declines. However, the effects of these therapies on diastolic function remain incompletely defined. METHODS: In a rigorously phenotyped, longitudinal cohort study of 362 breast cancer participants treated with doxorubicin, doxorubicin followed by trastuzumab, or trastuzumab alone, changes in diastolic function were evaluated using linear models estimated via generalized estimating equations. Associations between baseline and changes in diastolic function with LVEF and longitudinal strain were also determined using generalized estimating equations. The Kaplan-Meier estimator derived the proportion of participants who experienced incident diastolic dysfunction. Cox proportional hazards models estimated the associations between participant characteristics and diastolic dysfunction risk, and between diastolic function and cancer therapy-related cardiac dysfunction risk, defined by an LVEF decline of ≥10% to <50%. RESULTS: Over a median of 2.1 years (interquartile range [IQR]: 1.3 to 4.2 years), participants treated with doxorubicin or doxorubicin followed by trastuzumab demonstrated a persistent worsening in diastolic function, with reductions in the E/A ratio, lateral and septal e' velocities, and increases in E/e' (p < 0.01). These changes were not observed with trastuzumab alone. Incident abnormal diastolic function grade occurred in 60% at 1 year, 70% by 2 years, and 80% by 3 years. Abnormal diastolic function grade was associated with a subsequent decrease in LVEF (-2.1%; 95% confidence intervals [CI]: -3.1 to -1.2; p < 0.001) and worsening in longitudinal strain (0.6%; 95% CI: 0.1 to 1.1; p = 0.013) over time. Changes in E/e' ratio were modestly associated with worsening longitudinal strain (0.1%; 95% CI: 0.0 to 0.2; p = 0.022). CONCLUSIONS: A modest, persistent worsening of diastolic function is observed with contemporary breast cancer therapy. Abnormal and worsening diastolic dysfunction is associated with a small risk of subsequent systolic dysfunction. (Cardiotoxicity of Cancer Therapy [CCT]; NCT01173341).