31. Neoadjuvant Endocrine Therapy in Breast Cancer Up-Regulates the Cytotoxic Drug Pump ABCG2/BCRP, and May Lead to Resistance to Subsequent Chemotherapy

Abstract

Background: Neoadjuvant endocrine therapy (NAET) for breast cancer is utilised to down-stage tumours, thereby increasing rates of breast conserving surgery. However, little is known about how NAET impacts on response to subsequent adjuvant therapies. Here, we investigate the relevance of expression of the xenobiotic transporter ABCG2/BCRP, a gene/protein associated with chemoresistance, in the context of NAET and particularly with reference to subsequent chemotherapy treatment after NAET.