Patient description: The patient is a 45-year-old postmenopausal woman with cytologically confirmed breast cancer. A core biopsy revealed a 3 cm invasive ductal breast carcinoma in the left upper outer quadrant. The tumor is HER2-positive and ER/PR negative. Axillary sampling revealed 5 positive lymph nodes. CXR was remarkable for metastatic lesions. The patient is using multivitamins and iron supplements. She does not smoke or consume alcohol. She is not sexually active and has no children. She is a candidate for tumor resection and agrees to do so prior to chemotherapy.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Breast Neoplasm Hormone Receptor Positive Breast Carcinoma Patients must have a diagnosis of HR+ breast cancer. To fulfill the requirement of HR+ disease, a breast cancer must express, by immunohistochemistry (IHC), at least one of the hormone receptors (ER, progesterone receptor [PgR]) as defined in the relevant American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) Guidelines (Hammond et al. 2010): 1. For ER and PgR assays to be considered positive, ≥1% of tumor cell nuclei must be immunoreactive by immunohistochemistry (IHC) (Hammond et al. 2010) Patients must have Loco regional breast cancer (Stage I, Stage II and stage III per AJCC 8th edition for staging of breast cancer) Patients must have localized recurrence while on adjuvant endocrine therapy Patients must have any known molecular evidence of endocrine resistance by next generation sequencing Age ≥ 18 years ECOG performance status 0-1 Have post-menopausal status as defined by following: 1. Prior bilateral oophorectomy 2. Age ≥ 60 years 3. Age < 60 and amenorrheic (non-treatment-induced amenorrhea secondary to tamoxifen, toremifene, ovarian suppression, or chemotherapy) for at least 12 months. Follicle-stimulating hormone (FSH) and estradiol must be in the postmenopausal range Have at least one measurable disease as defined per 1.1 Adequate organ and marrow function as defined below: 1. Hemoglobin* > 8 g/dL 2. Absolute neutrophil count ≥ 1,500/mcL 3. Total bilirubin ≤ 1.5 X institutional ULN, Patients with Gilbert's syndrome with a total bilirubin ≤2.0 times ULN and direct bilirubin within normal limits are permitted 4. AST (SGOT)/ALT (SPGT) ≤ 2.5 X institutional ULN 5. Creatinine ≤ 1.5 X institutional ULN 1. *Patients may receive transfusion of packed red blood cells (PRBC) to achieve this hemoglobin level at the discretion of the investigator; however, initial study drug treatment must not begin earlier than the day after the PRBC transfusion Able to swallow oral medications  Stage IV metastatic breast cancer 1. This study will utilize the American Joint Committee on Cancer (AJCC) staging system, eight edition that provides a strategy for grouping patients with respect to prognosis. The AJCC has designated staging by TNM classification. The researchers will also review tumor size, lymph node status, and estrogen-receptor and progesterone-receptor levels in the tumor tissue Patients with HER2 positive and triple negative breast cancer 1. To fulfill the requirement of HER2 and Triple negative disease, a breast cancer must not demonstrate, at initial diagnosis or upon subsequent biopsy, overexpression of HER2 or should not express ER or PR receptors by either IHC or in-situ hybridization (ISH) as defined in the relevant ASCO/CAP guidelines (Wolff et al. 2013) Inflammatory breast cancer Newly diagnosed endocrine naïve patients No molecular evidence of endocrine resistance Prior treatment with any CDK 4/6 inhibitor and/or Fulvestrant Pre-menopausal women Are currently receiving an investigational drug in a clinical trial or participating in any other type of medical research judged not to be scientifically or medically compatible with this study. If a patient is currently enrolled in a clinical trial involving non-approved use of a device, then agreement with the principal investigator is required to establish Have had major surgery within 14 days prior to enrollment to allow for post-operative healing of the surgical wound