The ADCC effect of trastuzumab as an additive mechanism of action to targeting HER2+ BC cells might be suggested by the EGF104900 clinical trial of lapatinib ± trastuzumab in metastatic BC patients that progressed to trastuzumab.24 This study shows the superiority of trastuzumab plus lapatinib combination over lapatinib alone in patients who progressed on trastuzumab-based therapy in terms of PFS (HR: 0.74; 95% CI: 0.58–0.94, p = 0.011) and OS (HR: 0.74; 95% CI: 0.57–0.97, p = 0.026). This evidence concerns the gene ERBB2 and breast cancer.