PRIMARY OBJECTIVE:~I. To identify predictive immune biomarkers and mechanisms of response to ribociclib or palbociclib in advanced, hormone receptor positive breast cancer patients.~SECONDARY OBJECTIVES:~I. Identify changes in antigen presentation machinery and costimulatory molecules on circulating myeloid cells as a result of ribociclib or palbociclib treatment.~II. Characterize the dynamic remodeling of circulating myeloid cell composition that occur as a result of ribociclib or palbociclib treatment.~III. Characterize acquired immune tumor microenvironment features of resistance in patients that progress while undergoing ribociclib or palbociclib treatment.~EXPLORATORY OBJECTIVE:~I. To study the association between immune biomarkers and clinical response.~OUTLINE: Patients are assigned to 1 of 2 cohorts.~PROSPECTIVE COHORT: Patients receive standard of care (SOC) treatment consisting of ribociclib or palbociclib plus aromatase inhibitor (AI). Patients undergo biopsy of tumor tissue at baseline and post-treatment. Patients also undergo collection of blood samples at baseline, on day 1 of SOC treatment cycles 2, 4, and 6, every 6 cycles thereafter, and at post-treatment.~RETROSPECTIVE COHORT: Patients' tumor tissue collected during previous SOC treatment (ribociclib or palbociclib plus AI) is used for analysis.
This clinical trial attempts to understand the differences between two chemotherapy drugs, ribociclib and palbociclib, and how they fight cancer. This study looks at tissue and blood characteristics of patients receiving these therapies in the hopes to develop a way to predict which medication would provide the most benefit to an individual patient.