FES PET/CT in Predicting Response in Patients With Newly Diagnosed Metastatic Breast Cancer Receiving Endocrine Therapy

• Patient must NOT be in liver failure as judged by the patient's physician
• Patient is not now, and never has received adjuvant endocrine therapy OR patient is currently receiving or has received adjuvant endocrine therapy in the past, AND adjuvant endocrine therapy was initiated \> 2 years prior to diagnosis of metastatic disease
• Note: patients who developed metastatic disease while still receiving adjuvant endocrine therapy must have a planned change in the type of endocrine agent used for subsequent metastatic disease treatment; patient is not receiving blocking adjuvant therapy (such as toremifene or tamoxifen) OR patient is receiving blocking adjuvant therapy, but will stop this therapy a minimum of 60 days prior to FES-PET/CT while still complying with the study timeline
• Disease may be measurable (by Response Evaluation Criteria in Solid Tumors \[RECIST\] 1.1 criteria) or non-measurable but must be present in at least one non-liver site, where presence is defined as 1.5 cm or greater and visualized on PET/CT with \[18F\]-fluorodeoxyglucose (FDG); patients with effusion only disease or disease only in the liver are not eligible for the study

Exclusion Criteria Not Yet Provided