Radiation Therapy, Palbociclib, and Hormone Therapy in Treating Breast Cancer Patients With Bone Metastasis

Patient Selection Guidelines:

• Patients must have the psychological ability and general health that permits completion of the study requirements and required follow up
• Women of childbearing potential who are sexually active should be willing and able to use medically acceptable forms of contraception during protocol treatment

Inclusion Criteria

• Pathologically confirmed metastatic breast cancer
• Known estrogen, progesterone, and human epidermal growth factor receptor 2 (Her2) status of either primary tumor or metastasis
• Metastatic estrogen receptor positive (ER+) or progesterone receptor positive (PR+), Her2/neu negative breast cancer patients with imaging confirming bone metastasis within 60 days of radiation simulation
• Must be actively receiving palbociclib (125 or 100 mg PO daily for 3 weeks followed by a week off during 28-day cycles) plus one of the following hormone therapies for at least 28 days:
• Fulvestrant (500 mg IM injection on days 1 and 15 cycle one and then on day one of each subsequent cycle (28 days) -or-
• Letrozole (2.5 mg PO daily) -or-
• Anastrozole (1 mg PO daily) -or-
• Exemestane (25 mg PO daily) -or-
• Tamoxifen (20 mg PO daily)
• Patients must be willing and able to provide written informed consent/assent for the trial
• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2
• Karnofsky performance status (KPS) ≥ 60% within 60 days prior to registration
• Must have bone disease that is either symptomatic (i.e. pain) or has a lytic or mixed lytic disease that can be assessed by computed tomography (CT), magnetic resonance imaging (MRI), bone scan or positron emission tomography (PET)/CT within 60 days prior to radiotherapy on this study
• One previous line of chemotherapy in advanced disease is allowed
• Appropriate stage for study entry based on the following diagnostic workup:
• History and physical examination within 60 days prior to registration
• Clinical grade CT scans of the chest, abdomen, and pelvis with radionuclide bone scan OR whole body PET/CT documenting metastatic disease prior to radiotherapy on this protocol or MRI documenting site of metastatic disease to be treated on protocol
• Patient must be eligible for palliative radiotherapy (conventional radiation either 30 Gy in 10 fractions or 20 Gy in 5 fractions) for up to 4 separate anatomic regions containing bone metastases defined by 4 separate and not overlapping radiation plans
• Absolute neutrophil count ≥ 1000/mcl (obtained within 14 days prior to registration on study)
• Platelets ≥ 75, 000 mm³ (obtained within 14 days prior to registration on study)
• Hemoglobin ≥ 8.0 g/dl (obtained within 14 days prior to registration on study) (Note: The use of transfusion or other intervention to achieve hemoglobin [Hgb] ≥ 8.0g/dl is acceptable) (obtained within 60 days prior to registration on study)
• For females of child-bearing potential, negative serum or urine pregnancy test within 14 days prior to radiation simulation
• The patient or a legally authorized representative must provide study-specific informed consent prior to study entry
• Prior Treatment:
• Patients may or may not have received radiotherapy or neoadjuvant or adjuvant chemotherapy in the treatment of their initial, non-metastatic breast cancer, but must be entered on study after their last dose of radiotherapy, last cycle of chemotherapy and biologic therapy (if applicable) and have sufficient resolution of side effects per physician assessment at time of radiotherapy
• Patients must have not active wound healing issues from surgery and sufficient resolution of surgical side effects, per physician assessment, at time of radiotherapy
• If patients have one line of chemotherapy for advanced disease, patients must be entered on study after their last dose of chemotherapy and have sufficient resolution of side effects per physician assessment at time of radiotherapy
• Patients must have already initiated palbociclib (3 weeks on, 1 week off) and hormon