Discordant Human Epidermal Growth Factor Receptor 2 and Hormone Receptor Status in Primary and Metastatic Breast Cancer and Response to Trastuzumab

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Abstract
Recent studies have shown that the human epidermal growth factor receptor 2 status of a metastatic site may differ from that of the primary site. This difference may influence patient prognosis and response to therapy. We conducted a retrospective study using immunohistochemistry and/or fluorescent in situ hybridization to compare human epidermal growth factor receptor 2 and hormone receptor status in primary and metastatic breast cancers. Fifty-six patients were included in this study. Conversion from hormone receptor positive in the primary tumor to hormone receptor negative in the metastasis occurred in 12 patients (21.4%), and hormone receptor negative to hormone receptor positive conversion occurred in two patients (3.6%). Human epidermal growth factor receptor 2 status was discordant between primary and metastatic lesions in seven patients (12.5%). All of the five patients who converted from human epidermal growth factor receptor 2 negative status to human epidermal growth factor receptor positive received trastuzumab-based chemotherapy. Overall response rate and median progression-free survival for concordant human epidermal growth factor receptor 2 positive patients were 69.2% and 16.9 months, whereas that of patients with positive conversion of human epidermal growth factor receptor 2 were 40.0% and 7.6 months, respectively (overall response rate; P = 0.169 and progression-free survival; P = 0.004). Discordance in human epidermal growth factor receptor 2 and hormone receptor status between primary and metastatic tumors was observed, which led to altered treatment decisions. Evaluation of human epidermal growth factor receptor 2 and hormone receptor in metastatic tumors should be considered in patients with breast cancer.

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