An Imaging Scan (FDG-PET/MRI) to Monitor Early Treatment Response in Women with Metastatic HER2 Positive Breast Cancer

Inclusion Criteria

• Patients must be >= 18 years old and =< 75 years old
• Patients with HER2+ metastatic breast cancer
• HER2-positive breast cancer prospectively determined on the primary tumor by a local pathology laboratory and defined as immunohistochemistry (IHC) score of 3+ and/or positive by in-situ hybridization (ISH) (defined by ISH ratio of >= 2.0 for the number of HER2 gene copies to the number of chromosome 17 copies). Only one positive result is required for eligibility
• Estrogen/progesterone receptor positive OR negative disease allowed
• Patients must have measurable disease > 2 cm in one metastatic lesion per RECIST version (v) 1.1
• Stage IV HER2+ breast cancer patients eligible for a new therapeutic regimen that includes HER2-targeted treatment who are naive to that regimen
• Estimated life expectancy of greater than six months

Exclusion Criteria

• Children, less than 18 years of age, will be excluded from this study
• Metastatic breast cancer patients who are HER2 positive and have already started their current HER2-targeted therapy regimen for metastatic disease
• Patients who have not recovered from grade 2 or higher toxicities of prior therapy to the point that they would be appropriate for re-dosing will be ineligible for study treatment
• Patient is pregnant or breastfeeding, or expecting to conceive children within the projected duration of the study, starting with the screening visit through 7 months after the last dose of study treatment
• Patient is considered a poor medical risk due to a serious, uncontrolled medical disorder, nonmalignant systemic disease or active infection that requires systemic therapy. Specific examples include, but are not limited to, active, non-infectious pneumonitis; uncontrolled major seizure disorder; unstable spinal cord compression; superior vena cava syndrome; or any psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the study (including obtaining informed consent)
• Patients found to have constitutionally present non-magnetic resonance (MR) compatible ferromagnetic materials
• Patients with lung nodules as the only location of measurable disease > 2 cm
• Unable to lie still on the imaging table for one (1) hour
• Inability to receive gadolinium-based contrast agent
• Patients for whom a PET/MRI is technically not feasible (e.g. breast volume, obesity, > body mass index [BMI] 36)