Evidence-based neoadjuvant endocrine therapy for breast cancer

Breast cancer is the most common malignancy among women in Western countries. The management of patients with nonmetastatic breast cancer with primary endocrine therapy has evolved dramatically in the past decade. Neoadjuvant treatment has been used to turn inoperable tumors into operable tumors and also to downstage tumors. Hormone receptor-positive breast tumors exposed to neoadjuvant chemotherapy have lower rates of pathologic complete response than hormone receptor-negative tumors. Recently, clinical trials showed an increased response rate and a higher rate of breast-conserving surgery with aromatase inhibitors compared with tamoxifen. Exploratory data suggest that predictive markers of response include a higher estrogen receptor expression level and a negative HER2 status. With the introduction of "biologic" agents and surrogate markers like Ki-67, several studies are evaluating which patients are more likely to respond to preoperative hormonal agents. This review summarizes recent data on neoadjuvant endocrine therapy for breast cancer and the implication of predictive markers of response into clinical practice and future research.