Receptor Conversion in Distant Breast Cancer Metastases: A Systematic Review and Meta-analysis

In metastatic breast cancer, hormone and/or human epidermal growth factor receptor 2 (HER2)–targeted therapy decision-making is still largely based on tissue characteristics of the primary tumor. However, a change of estrogen receptor alpha (ERα), progesterone receptor (PR), and HER2 status in distant metastases has frequently been reported. The actual incidence of this phenomenon has been debated. We performed a meta-analysis including 39...