Exemestane With or Without Entinostat in Treating Patients With Recurrent Hormone Receptor-Positive Breast Cancer That is Locally Advanced or Metastatic

PRIMARY OBJECTIVES: I. To evaluate whether the addition of entinostat to endocrine therapy (exemestane) improves progression-free survival (PFS) and/or overall survival (OS) in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer who have previously progressed on a non-steroidal aromatase inhibitor (Al). SECONDARY OBJECTIVES: I. To evaluate the safety and tolerability of entinostat in combination with exemestane, and to compare the safety profile to that of endocrine therapy with placebo. II. To evaluate the objective response rate of exemestane in combination with entinostat or placebo. III. To evaluate whether the efficacy of exemestane with entinostat varies with changes in acetylation status in peripheral blood mononuclear cells (PBMCs). IV. To evaluate the time to treatment deterioration (as defined by decrease in health-related quality of life \[HRQL\], progression, death) of exemestane + entinostat versus exemestane + placebo arms. V. To evaluate the differences in overall health-related quality of life (HRQL) between the exemestane + entinostat versus exemestane + placebo arms. VI. To evaluate the difference with respect to specific symptoms that are associated with entinostat, i.e., fatigue, nausea, anorexia and diarrhea, between the exemestane + entinostat versus exemestane + placebo arms. VII. To measure adherence to protocol therapy. VIII. To evaluate the pharmacokinetics of entinostat in patients with advanced breast cancer. IX. To evaluate what, if any, patient variables alter the pharmacokinetic profile of entinostat in patients with advanced breast cancer. EXPLORATORY OBJECTIVES: I. To collect archival tumor samples and germline deoxyribonucleic acid (DNA) to explore other potential biomarkers of therapeutic efficacy. II. To collect patient ratings of adverse events (AEs) using select patient-reported outcomes (PRO)-Common Terminology Criteria for Adverse Events (CTCAE) items to evaluate the psychometric properties of PRO-CTCAE items and explore the incorporation of PRO-CTCAE items into a phase III double-blind placebo-controlled trial. OUTLINE: Patients are randomized to 1 of 2 treatment arms. ARM A: Patients receive exemestane orally (PO) once daily (QD) on days 1-28 and entinostat PO on days 1, 8, 15, and 22. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients also undergo computed tomography (CT) or magnetic resonance imaging (MRI) at baseline, at the end of cycle 3, every 3 cycles, at treatment discontinuation, and during follow-up, collection of blood samples at baseline and day 15 of cycle 1, and collection of archived tissue at baseline. ARM B: Patients receive exemestane as in Arm A and placebo PO on days 1, 8, 15, and 22. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients also undergo CT or MRI at baseline, at the end of cycle 3, every 3 cycles, at treatment discontinuation, and during follow-up, collection of blood samples at baseline and day 15 of cycle 1, and collection of archived tissue at baseline. In both arms, pre/perimenopausal female patients and all male patients also receive goserelin acetate subcutaneously (SC) on day 1. After completion of study treatment, patients are followed up every 3 months for 2 years, every 6 months for 3 years, and then annually for 5 years.