Open-label Phase II study of everolimus plus endocrine therapy in postmenopausal women with ER-positive and HER2-negative metastatic breast cancer (Chloe trial)

Background: This is a randomized, multicenter, open-label, Phase II study designed to evaluate the efficacy of everolimus added to continuous aromatase inhibitor (AI) administration in patients who had maintained stable disease or a better response for at least 5 months. Patients and methods: Patients will be randomized to everolimus and standard therapy groups (1:1 ratio). In the everolimus group, patients will receive everolimus in addition to the AI agent. The standard therapy group will continue AI alone treatment. The primary endpoint is progression-free survival. Target accrual is 130 patients with a two-sided type I error rate of 10% and 80% power to detect 35% risk reduction. Conclusion: The Chloe trial will provide important information about the efficacy and safety of adding everolimus to AI in patients with estrogen receptor-positive and human epidermal growth factor 2-negative metastatic breast cancer.