Dose Optimization of Rosuvastatin in Early Stage and Metastatic Estrogen Receptor Positive Breast Cancer Patients on Endocrine Therapy

Patients will be treated in a dose escalation scheme to investigate a role for the addition of a statin in the treatment of estrogen receptor positive breast cancer. Patients will take oral rosuvastatin daily. The maximum number of patients evaluable for a DLT is 12. Dosing will be as follows: Cohort 1 - rosuvastatin 20mg, Cohort 2 - rosuvastatin 40mg. The patients will have a total of 4 blood draws and 4 breast biopsies. The breast biopsies will be collected to evaluate cholesterol metabolites and tumor microenvironment characteristics including gene expression profiling and metabolomics. Sampling will occur at study entry, week 4, week 8, and at the time of surgery in early stage patients or at week 16 for metastatic patients. Patients will begin endocrine therapy following the acquisition of week 4 samples (blood and tissue biopsy).