ERBB2 and breast cancer: Numerous clinical phase I and II trials evaluating the safety of lapatinib in patients with progressive or metastatic HER2 BC have shown that the incidence of left ventricular dysfunction ranges from 0 to 26.6%, with a decrease in LVEF of ≥20% or a post-treatment assessment of LVEF <50%, ranging from 0 to 12.8% (61).