Based on clinical studies, the 5th European School of Oncology and the European Society of Medical Oncology guidelines for advanced breast cancer (ABC 5) and the National Comprehensive Cancer Network guidelines consider trastuzumab (anti-HER2 domain IV mAb), pertuzumab (anti-HER2 domain II mAb), and docetaxel as the standard of care for first-line treatment of HER2-positive metastatic breast cancer [29]. The gene discussed is ERBB2; the disease is breast cancer.