68-Ga-RM2 PET/MRI in Imaging Patients With Estrogen Receptor-Positive Breast Cancer

Inclusion Criteria:

   - ER+ breast cancer at initial diagnosis prior to surgery or at recurrence (at least one
   ER+ lesion based on results of biopsy).

   - Able to provide written consent

   - Karnofsky performance status of ≥ 50 (or Eastern Cooperative Oncology Group
   (ECOG)/World Health Organization (WHO) equivalent)

Exclusion Criteria:

   - Less than 18 years-old at the time of radiotracer administration

   - Inability to lie still for the entire imaging time

   - Inability to complete the needed investigational and standard-of-care imaging
   examinations due to other reasons (severe claustrophobia, radiation phobia, etc.)

   - Any additional medical condition, serious intercurrent illness, or other extenuating
   circumstance that, in the opinion of the Investigator, may significantly interfere
   with study compliance

   - Renal function impairment preventing administration of MRI contrast

   - Metallic implants (contraindicated for MRI)