Trastuzumab and antiestrogen therapy -: Focus on mechanisms of action and resistance

Objective: In breast cancer, 2 molecular targets are well established (ER/PR and HER2), and therapies directed to these proteins have demonstrated to be clinically useful. Methods: Despite the presence of the ER and PR, only half of the patients will respond to endocrine therapy, and less than 35% of patients with ErbB2-overexpressing metastatic breast cancer will respond to trastuzumab as a single agent. Results: To improve survival of metastatic breast cancer patients with ER/PR positive and HER2 positive is critical to elucidate the mechanism of resistance or sensitivity of these tumors for a better selection depending on biologic molecular alterations. Conclusions: Recently, several studies addressing this issue have been reported. Here, we will focus on a comprehensive review of the currently available data.