HER-3 status by immunohistochemistry in HER-2-positive metastatic breast cancer patients treated with trastuzumab: correlation with clinical outcome.

Aims And Background: HER-3 signaling might contribute to resistance to trastuzumab. To clarify the role of HER-3 in HER-2-positive breast cancer, it is important to evaluate the level of HER-3 and its correlations with clinical outcome in metastatic breast cancer patients treated with trastuzumab.

Methods: HER-3 status by immunohistochemistry was evaluated in HER-2-positive metastatic breast cancer patients treated with trastuzumab-based therapy at our institution.