An Investigational Scan (64Cu-DOTA-Trastuzumab PET/MRI) in Imaging Patients With HER2+ Breast Cancer With Brain Metastasis

This clinical trial examines an investigational scan (64Cu-DOTA-trastuzumab positron emission tomography \[PET\]/magnetic resonance imaging \[MRI\]) in imaging patients with HER2+ breast cancer that has spread to the brain (brain metastasis). Diagnostic procedures, such as 64Cu-DOTA-trastuzumab PET/MRI, may help find HER2+ breast cancer that has spread to the brain and determine whether cancer in the brain takes up trastuzumab, which may predict for response to trastuzumab deruxtecan (the standard of care chemotherapy).

Inclusion Criteria: * Documented informed consent of the participant and/or legally authorized representative * Women with documented metastatic HER2 positive breast cancer (American Society of Clinical Oncology \[ASCO\] College of American Pathologist \[CAP\] guidelines) who have brain metastases * Age \> 18 years * Eastern Cooperative Oncology Group (ECOG) 0-2 * Patients with leptomeningeal disease will be considered eligible * Planned therapy with fam-trastuzumab deruxtecan * Left ventricular ejection fraction (LVEF) \> 50% * Absolute neutrophil count (ANC) \> 1.5 x 10\^9/L * Platelets \> 100 x 10\^9/L * Hemoglobin \> 9 g/dL * Total (T.) bilirubin \< 3 x upper limit of normal (ULN) * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 5 x ULN * Creatinine clearance \> 30 ml/min (by Cockcroft-Gault formula) * Activated partial thromboplastin time (aPTT) \< 1.5 x ULN * Prior therapy for central nervous system (CNS) disease is allowed, but at least 1 lesion \> 1.5 cm is evident on MRI Exclusion Criteria: * Need for immediate local intervention for brain metastases * Noninfectious interstitial lung disease or pneumonitis requiring glucocorticoids * Clinically significant corneal disease * Myocardial infarction \< 6 months before, congestive heart failure (CHF), unstable angina, or serious cardiac arrhythmia