FDG PET to Assess Therapeutic Response in Patients with Bone-dominant Metastatic Breast Cancer, FEATURE

This phase II trial studies how well FDG-PET/CT works in assessing the response of patients
with breast cancer that has spread to the bones or mostly to the bones (bone-dominant
metastatic breast cancer). Diagnostic procedures, such as FDG-PET/CT, may work better in
measuring breast cancer activity before and after treatment compared to other standard
imaging tests.

Inclusion Criteria:

- Patients must have an Eastern Cooperative Oncology Group (ECOG) performance
(performance status [PS]) =< 2

- Patients with histologically confirmed metastatic breast cancer by local assessment
that is hormone receptor positive by American Society of Clinical Oncology
(ASCO)/College of American Pathologists (CAP) guidelines and with known HER2 status

- Patients must have radiologically confirmed bone-dominant (BD) or bone-only (BO)
disease

- BD defined as disease involving bone with or without limited measurable
metastases by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, with >=
1 non-irradiated bone metastasis on bone scintigraphy

- NOTE: Limited measurable metastases includes lymph nodes and the soft tissue
components of lytic or mixed lytic/blastic bone metastases. Any number of
lymph nodes < 3 cm and up to 2 lymph nodes > 3 cm will be allowed. Up to 5
measurable soft tissue components of lytic or mixed mytic/blastic bone
metastases will be allowed

- BO defined as detectable disease confined within the bone (any site, any number
of lesions). Diagnosis requires abnormalities identified by imaging (bone scan,
CT +/- PET +/- magnetic resonance imaging [MRI]) with no other sites of
metastases identified and with >= 1 non-irradiated bone metastasis on bone
scintigraphy

- Patients must have no contraindication to FDG-PET imaging

- Patients must have one of the following systemic therapies:

- Plan to receive either 1st or 2nd line endocrine therapy for metastatic breast
cancer. Endocrine therapy may include selective estrogen receptor modulators
(SERMs), aromatase inhibitors, and/or fulvestrant that may be combined with Food
and Drug Administration (FDA)-approved biologic agents (palbociclib, ribociclib,
abemaciclib, everolimus, alpelisib)

- Chemotherapy per National Comprehensive Cancer Network (NCCN) or institutional
standard. Use of colony stimulating growth factor must be suspended for >= 14
days prior to FDG-PET/CT scans at baseline and 12-weeks

- Plan to receive HER2-targeted therapy per ASCO, NCCN, and/or institutional
guidelines as indicated for patients with HER2 positive disease. When
HER2-targeted therapy is used with chemotherapy, use of colony stimulating growth
factors is NOT expected or should be suspended for a minimum of 2 weeks, but
preferably for at least 3 weeks prior to the required FDG-PET/CT scan time points

- The use of bone-stabilizing agents (bisphosphonates or denosumab) is permitted

- Patient must meet institutional guidelines for renal function for MRI and CT scanning

- Patient's life expectancy must be estimated at >= 24 weeks

- The patient is participating in the trial at an institution which has agreed to
perform the imaging research studies, completed the ECOG-American College of Radiology
Imaging Network (ACRIN) defined PET/CT scanner qualification procedures and received
ECOG-ACRIN PET/CT scanner approval

- Patients must complete the baseline (T0) FDG-PET within 28 days prior to registration
or within 28 days after registration

- For patients completing the baseline (T0) FDG-PET AFTER registration all
parameters must be met

- For patients who completed the baseline (T0) FDG-PET prior to registration the
following tests are exempt:

- Pregnancy testing documentation prior to FDG-PET (T0 time point)

Exclusion Criteria:

- Patients with RECIST 1.1 measurable lesions in viscera, active central nervous system
(CNS), leptomeningeal carcinomatous or pleural or peritoneal disease will not be
eligible. Patients with prior CNS metastases treated with radiation or resection and
without evidence of clinical or radiographic progression within 28 days of
registration are eligible

- Patients who have received greater than 3 lines of cytotoxic chemotherapy for
metastatic breast cancer are not eligible

- Patients currently participating in or have participated in a study of an
investigational agent or using an investigational device within 3 weeks of study
registration are not eligible

- Patients with known additional malignancy that is progressing or requires active
treatment are not eligible. Exceptions include basal cell carcinoma of the skin,
squamous cell carcinoma of the skin, or in situ cervical cancer that has undergone
potentially curative therapy

- Women must not be pregnant because FDG is a radiopharmaceutical with the potential for
teratogenic effects and PET/CT involves additional radiation exposure. In addition,
because of radiation exposure to a nursing infant from FDG, women who are
breastfeeding are also excluded from this study. All females of childbearing potential
must have a blood test or urine study within 7 days prior to FDG-PET/CT to rule out
pregnancy. Patients are excluded from this if baseline FDG-PET/CT scan met study
parameters and was completed within 28 days of study registration