Mild Cardiotoxicity and Continued Trastuzumab Treatment in the Context of HER2-Positive Breast Cancer.

Breast cancer is the leading cause of cancer death in women worldwide. Trastuzumab, the main HER2-targeted treatment, faces limitations due to potential cardiotoxicity. The management of patients with mild cardiotoxicity on trastuzumab remains uncertain, resulting in treatment discontinuation and negative oncological outcomes. This retrospective study analyzed 23 patients who experienced decreased left ventricular function during trastuzumab treatment. During the 18-month follow-up period, two patients (9%) had severe declines in function, leading to treatment cessation, and one patient (4%) developed heart failure symptoms. However, 21 patients showed mild, reversible myocardial dysfunction without significant differences in final ventricular function compared to a control group (58.4% vs. 61.7%, respectively; p = 0.059). The declines in function were most pronounced at nine months but improved at twelve and eighteen months. Various echocardiographic parameters changed significantly over time. As predictors of severe cardiotoxicity, we identified the following: LVEF before initial chemotherapy (p = 0.022), as well as baseline LVEF before treatment with trastuzumab (p = 0.007); initial left ventricular end systolic volume (p = 0.027); and the initial global longitudinal strain (p = 0.021) and initial velocity time integral in the left ventricular outflow track (p = 0.027). In conclusion, the continuation of trastuzumab should be considered for most patients with mild cardiotoxicity, with close cardiac monitoring and cardioprotective measures. However, identifying the patients at risk of developing severe cardiotoxicity is necessary. According to our data, the initial LVEF and GLS levels appear to be reliable predictors.