Clinical Utility of FES F18 PET/CT in Metastatic Breast Cancer Patients

Inclusion Criteria: * Patient must sign informed consent prior to enrollment in this trial * The patient is a female ≥18 years old * Post-menopausal or pre-menopausal patient with known primary breast tumor(s) expressing ER in ≥1% of tumor cells by IHC * HER2-negative (0, 1+, 2+ fluorescence in situ hybridization (FISH) negative) primary lesion * MBC with at least 1 identifiable lesion on standard-of-care imaging assessment, outside of the liver, as confirmed by the investigator site * Patient with progressive disease on 1st line hormonal therapy (Aromatase Inhibitor) with or without a CDK4/6 inhibitor or mechanistic target of rapamycin (mTOR) inhibitor or phosphoinositide 3-kinases (PI3K) inhibitor * Patient must score at least 0, 1 or 2 on the Eastern Cooperative Oncology Group (ECOG) Performance Status * Life expectancy of at least 12 months * The patient is planned to undergo a standard-of-care imaging scan (according to National Comprehensive Cancer Network guidelines, e.g., CT and/or bone scan, or fluorodeoxyglucose \[FDG\]-PET/CT) covering chest, abdomen, and pelvis after date of consent and before Cerianna PET/CT (Visit 2), or the patient has undergone recent standard-of-care imaging before date of consent and is planned to undergo Cerianna PET/CT (Visit 2) no more than 45 days from the standard-of-care imaging scan Exclusion Criteria: * Isolated hepatic metastases (taking into account the physiological hepatic high uptake of Cerianna) * Patient is on tamoxifen/toremifene treatment without 8-week washout, or on fulvestrant treatment without 28-week washout, (may block ER) before Cerianna PET/CT * Other evolutive malignant disease (non-melanoma skin cancer is allowed) or acute or chronic infectious disease (well-controlled infectious disease is allowed); * Patient has a history of administered chemotherapy for metastatic disease; prior chemotherapy in the (neo)adjuvant setting is allowed * Patient with a known allergy to any of the components of Cerianna * Woman of childbearing age who is not using effective contraception * Pregnant woman (per the Product Label and ensured using clinic's standard-of-care), or parturient or nursing mother * Patient presents with any other clinically active, serious, life-threatening disease, medical, or psychiatric condition, and/or who has a life expectancy of \<12 months, or for whom study participation may compromise their management; and/or a patient who the investigator judges to be unsuitable for participation in the study for any reason * Inability to comply with any requirements of the protocol