This trial studies how well 68-Ga RM2 works with PET/MRI in imaging patients with estrogen receptor-positive breast cancer. 68-Ga-RM2 is an agent used in diagnostic imaging.

PRIMARY OBJECTIVES:

I. To evaluate the feasibility of 68-Ga RM2 PET/MRI for identification of estrogen receptor positive primary breast cancer and metastases

OUTLINE:

Patients receive 68-Ga-RM2 intravenously (IV) and after 45 minutes undergo PET/MRI over 30-60 minutes.

After completion of study, patients are followed up at 24-72 hours, and then for 12 months.

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)