ERBB2 and metastatic neoplasm: Human epidermal growth factor receptor 2 (HER2)-positive and hormone receptor (HR)-positive breast cancer is a special type of breast cancer, representing an estimated 10% of all breast cancer subtypes.[1] For patients with advanced or metastatic disease, chemotherapy plus HER2 targeted therapy is commonly recommended as a first-line treatment according to current international guidelines.[2] However, some patients cannot tolerate the toxicity of chemotherapy because of their poor physical condition.