Left atrial volume in patients with HER2‐positive breast cancer: One step further to predict trastuzumab‐related cardiotoxicity

Background Trastuzumab (TZ) therapy requires careful monitoring of left ventricular (LV) ejection fraction (LVEF) because it can be potentially cardiotoxic. However, LVEF is an imperfect parameter and there is a need to find other variables to predict cardiac dysfunction early. Left atrium (LA) enlargement has proven to be a powerful predictor of adverse outcomes in several disease entities. Hypothesis Baseline LA volume enlargement might predict TZ‐related LV dysfunction. Methods HER2‐positive breast cancer patients receiving TZ and undergoing transthoracic echocardiography at baseline and at follow‐up every 3 months were retrospectively recruited. One‐hundred sixty‐two patients formed the study population. Results Baseline LAVI was dilated in 14 patients (8.6%). Mean follow‐up was 14 ± 4 months. Cardiotoxicity occurred in 24 patients (14.8%). LAVI was an independent predictor of TZ‐induced LV dysfunction in a clinical model, after adjustment for age and hypertension (odds ratio per 5‐mL/m 2 LAVI increase: 1.34, 95% confidence interval: 1.03‐1.82, P = 0.03); and in a hemodynamic model, including ventricular sizes and systolic blood pressure level (odds ratio per 5‐mL/m 2 LAVI increase: 1.34, 95% confidence interval: 1.01‐1.81, P = 0.04). The predicted probability of developing cardiotoxicity increased progressively, in parallel with LAVI values. Conclusions Baseline LA dilatation emerges as a condition associated with the development of cardiotoxicity in HER2‐positive breast cancer patients treated with TZ.