Background
MBC, HR-positive
METASTATIC BREAST CANCER
Human epidermal growth factor receptor 2 (HER2) targeted therapy combined with endocrine therapy has been recommended as an alternative treatment strategy for patients with hormone receptor (HR)-positive, HER2-positive metastatic breast cancer (MBC). This study aimed to evaluate the role of pyrotinib, an oral pan-HER irreversible tyrosine kinase inhibitor, in combination with letrozole for patients with HR-positive, HER2-positive MBC.