ERBB2 and breast cancer: In a study examining patients with stage I and II BC treated between 1975 and 1981, those with HER2-positive disease had the worst survival rates regardless of hormone receptor status.4 Decades later, a study that evaluated patients with metastatic BC (mBC) diagnosed between 2004 and 2007 found that patients with HER2-positive disease had the most favorable survival rates.5 In addition to managing the disease, an important part of the mBC treatment plan consists of preventing, monitoring for, and managing treatment-related adverse events (AEs).