Study of Dotatate Imaging in Breast Cancer

Inclusion Criteria: * Age of at least 18 years at the time of signing the informed consent. * Biopsy proven, ER+, HER2 any, clinically progressive, Stage IV breast cancer requiring restaging. * For women of childbearing potential (WOCBP): a. Negative serum pregnancy test within 48 hours of Ga-68-DOTATATE injection. A women is considered to be of childbearing potential if she is post-menarchal, has not reached postmenopausal state (≥ 12 continuous months of amenorrhea \[no menstrual bleeding of any kind, including menstrual period, irregular bleeding, spotting, etc.\] with no identified cause other than menopause), and has not undergone surgical sterilization (total hysterectomy, or bilateral tubal ligation or bilateral oophorectomy at least 6 weeks before taking study drug). * Willingness and ability to provide written informed consent prior to any study-specific assessments and procedures commence. Exclusion Criteria: * Known hypersensitivity to Gallium-68 DOTATATE or Copper-64 DOTATATE, octreotate, or any of the excipients of Gallium-68 DOTATATE or Copper-64 DOTATATE * Current high-dose glucocorticoid (≥ 20 mg prednisone daily or equivalent); long acting SSA within the last 28 days; short acting SSA that cannot be interrupted for 24 hours. * Unable to perform PET/CT scans according to technical specifications and local guidelines. * Concurrent primary malignancy, except adequately treated carcinoma in situ, non-melanoma carcinoma of the skin or any other curatively tr…