Inclusion Criteria:

          -  Women with ER+/PR+ HER2-negative breast cancer initiating neoadjuvant endocrine
             therapy with curative intent OR initiating endocrine therapy for the treatment of
             metastatic breast cancer with a biopsy accessible primary breast tumor

          -  The patients may start any FDA approved endocrine therapy (with which they have not
             been previously treated) at week 4 of the trial except for tamoxifen

          -  Palbociclib can be started at week 4, if indicated

          -  Patients with metastatic disease currently on endocrine therapy must be willing to
             stop endocrine therapy for 2 weeks prior to starting the study and to switch to a new
             endocrine therapy on the study (at week 4)

          -  Intact breast tumor present and size measuring at least 1cm at enrollment

          -  Post-menopausal at enrollment (age ≥ 60, age ≤ 60 and amenorrhea for ≥12 months in the
             absence of chemotherapy, tamoxifen, ovarian suppression and FSH/estradiol in the
             post-menopausal range)

          -  ECOG ≤ 2

          -  Can be on other endocrine therapy if willing to change a different endocrine therapy
             agent for the trial

          -  Must have at least one FDA approved endocrine therapy option with which the patient
             has not received prior treatment

          -  Life expectancy > 12 weeks

          -  Laboratory criteria: normal renal function: creatinine < 1.5 x upper limit of normal
             (ULN)), liver function: bilirubin < 2 x ULN, transaminases < 2 x ULN and blood counts:
             WBC ≥ 2.0, Neutrophils ≥1250, platelets ≥50,000, Hemoglobin ≥ 8.

          -  Age > 18 years

          -  Patients must have the ability to give informed consent.

          -  Patients must have a signed informed consent form prior to enrollment on study. -

        Exclusion Criteria:

          -  Statin use in the last 6 months

          -  Patient has been treated with all FDA approved endocrine therapies or has been treated
             with all FDA approved endocrine therapies except for tamoxifen (tamoxifen is excluded
             from the trial)

          -  Active liver disease with elevated transaminases > 2x ULN

          -  Known hypersensitivity to rosuvastatin

          -  Any history of any other cancer (except non-melanoma skin cancer or carcinoma in-situ
             of the cervix) unless the patient has been in remission and off all other cancer
             therapy for at least 3 years.

          -  Patients should have no significant psychiatric illness or medical illness that would
             preclude the ability to comply with the protocol.

          -  Patients currently taking medications with known rosuvastatin interactions including
             cyclosporine, gemfibrozil, lopinavir/ritonavir, atazanavir/ritonavir, coumarin
             anticoagulants, colchicine, fenofibrates, and niacin.