Fulvestrant or Aromatase Inhibitor and Palbociclib in Treating Older Patients With Hormone Responsive Breast Cancer That Cannot Be Removed by Surgery

Inclusion Criteria:

Newly diagnosed invasive, estrogen receptor (ER) and/or progesterone receptor (PR)-positive, HER2 negative breast cancer; ER-and/or PR-positive breast cancer is defined by > 10% staining by immunohistochemistry
Patients must be vulnerable or frail by Balducci Criteria or the patient is refusing breast surgery; vulnerable patients are defined as those with dependence in some instrumental activities of daily living, well controlled co-morbidities, and early symptoms of geriatric syndrome; frail patients are defined as those with three or more co-morbidities, dependence in one or more activities of daily living, or a clinically significant geriatric syndrome; geriatric syndromes include: dementia, delirium, incontinence (fecal and/or urinary), osteoporosis or spontaneous fractures, polypharmacy, visual/hearing impairment, sarcopenia and neglect or abuse
The patient's refusal to proceed with curative breast surgery has to be documented by the surgeon's and medical oncologist's note
Absolute neutrophil count (ANC) > 1000/uL
Platelets > 75,000/L
Serum creatinine 1.5 X institutional upper limit of normal (ULN)
Total bilirubin < 1.5 X ULN
Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) 2.5 ULN
Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

Prior aromatase inhibitor therapy
Evidence of distant metastases
Psychiatric illness, which would prevent the patient from giving informed consent
Patients receiving strong inducers or inhibitors of cytochrome P450 3A4 (CYP3A4)