Randomized phase II trial of preoperative fulvestrant with or without enzalutamide for ER+/Her2- primary breast cancer

Most ER+ breast cancers (BC) express androgen receptors (AR). This randomized phase II trial of 4 months of neoadjuvant fulvestrant (Fulv) alone or with enzalutamide (Combo) was performed to determine if the addition of AR blockade to Fulv would increase the percentage of patients with limited residual tumor at time of surgery, as measured by modified preoperative endocrine predictive index (PEPI) score. Eligible patients were women with ER+/HER2- primary BC cT2 or greater. Stratification factors were clinical node and T-stage. Fresh tumor biopsies were required at study entry, after 4 weeks on therapy (W5), and at surgery (week 17).