Significant response to the combination of pyrotinib and letrozole in a patient with metastatic HER2-positive and hormone receptor-positive breast cancer: a case report

Breast cancer is the most commonly diagnosed malignant tumor and leading cause of cancer-related death in women worldwide. Previous studies have demonstrated that patients with human epidermal growth factor receptor 2 (HER2)-positive/hormone (HR)-positive metastatic breast can benefit from HER2-targeted therapy. Pyrotinib, an irreversible tyrosine kinase inhibitor (TKI), has been to be effective safe treating HER2-positive patients. Letrozole aromatase (AI) which shown better clinical efficacy when combined HER2 inhibitors HR-positive than hormonal therapy alone. However, effect combination pyrotinib plus letrozole HER2-positive/HR-positive not yet investigated. In this case report, a 57-year-old female patient received modified radical mastectomy experienced subsequent relapse metastasis. She was relapsed right cancer, chest bone mass accompanied by destruction, metastases wall both lungs. then enrolled phase II trial treated letrozole, achieved durable response. Our shows may provide significant for tolerable adverse events.