Single Cell Immune and Non-immune Correlates of Response to Neoadjuvant Abemaciclib

The purpose of this study is to better understand how the immune system plays a role in fighting breast cancer and specifically research if the immune system response against breast cancer can be improved with endocrine therapy and cyclin dependent kinase inhibitor therapy in patients with hormone receptor positive breast cancer. This will be studied by collecting tumor tissue and blood samples before and after 2 weeks of study treatment with commonly used endocrine therapy and cyclin dependent kinase inhibitor therapy.