Observational study of trastuzumab-related cardiotoxicity in early and metastatic breast cancer.

Introduction Trastuzumab-related cardiotoxicity has been a major concern in clinical practice, since observational studies have shown higher incidences than that reported in clinical trials. We aim to measure the incidence of trastuzumab-related cardiotoxicity in patients with early and metastatic breast cancer in the south of Brazil. Methods Multicenter prospective observational study, which included 109 patients with early or metastatic HER-2+ breast cancer undergoing any trastuzumab-based regimen. Cardiac events were measured by transthoracic echocardiography assessments and by signs and symptoms of heart failure. Results Trastuzumab-related cardiotoxicity was observed in 58 patients (53.2%). Emergency and hospitalization admissions were necessary in seven and three patients, respectively, due to symptoms of heart failure. One patient died in consequence of trastuzumab-related cardiotoxicity. In total, trastuzumab was discontinued in 31.2% of patients, of which almost a third could not return to treatment. In this study, no risk factors were significantly associated with the development of cardiotoxicity. Discussion The incidence of TRC and trastuzumab's early discontinuation observed was significantly higher in comparison with other studies. These findings endorse the fact that trastuzumab-related cardiotoxicity is a relevant adverse reaction, and therefore, cardiac dysfunction's monitoring must be highlighted in order to allow a safe use of trastuzumab in this population.