Monitoring HER2+ Breast Cancer Neoadjuvant Treatment With Advanced PET/MRI

Inclusion Criteria: 1. Patients must be ≥ 18 years old and ≤ 75 years old 2. HER2+ breast cancer determined on primary tumor by a local pathology laboratory and defined as IHC score 3+ and/or positive by 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 3. Locally advanced stage II-III HER2+ breast cancer patients eligible for neoadjuvant therapy who are naïve to beginning treatment 4. Estimated life expectancy of greater than one year 5. Patients must have one lesion with RECIST measurable disease (great than 1 cm in diameter) Exclusion Criteria: 1. Inability to provide informed consent F 2. Weight over 350 lbs., due to the scanner bore size 3. Lactating, known or suspected pregnancy. Women with child-bearing potential must a have a negative serum β-hCG pregnancy test within 48 hours or a negative urine β-hCG pregnancy test within 48 hours of each PET imaging study. 4. Contraindication for MRI study (e.g. non-removable metal implants or certain tattoos) 5. Unable to lie still on the imaging table for one (1) hour 6. contraindication for gadolinium-based contrast agent, ProHance (gadoteridol)