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

This study is using advanced PET/MRI imaging to track how well treatment is working in people with HER2-positive breast cancer receiving chemotherapy and targeted therapy before surgery. Researchers want to know if these scans can predict which patients will have a complete response to treatment, helping personalize care. **You may be eligible if...** - You are between 18 and 75 years old - You have been diagnosed with locally advanced (stage II or III) HER2-positive breast cancer - You are about to begin pre-surgery (neoadjuvant) treatment for the first time - You have at least one tumor that is measurable on a scan (larger than 1 cm) - Your expected survival is more than one year **You may NOT be eligible if...** - You are pregnant, breastfeeding, or of childbearing potential without a negative pregnancy test - You weigh more than 350 lbs (scanner limitation) - You cannot lie still for 1 hour - You have metal implants or other contraindications to MRI - You are allergic to the MRI contrast agent Talk to your doctor to see if this trial is right for you.