Copper Cu 64-DOTA-Trastuzumab PET in Predicting Response to Treatment With Ado-Trastuzumab Emtansine in Patients With Metastatic HER2 Positive Breast Cancer

Inclusion Criteria:

* Participants must be women who have histological confirmation of metastatic invasive breast cancer that has metastasized outside the region of the primary tumor and axilla; biopsy must be obtained prior to initiation of chemotherapy; it should be performed within 28 days prior to enrollment (patients with a biopsy of recurrent disease that is HER2-positive and have not received HER2-directed therapy since the biopsy can exceed the 28-day window up to 6 months); patients must have metastatic disease in lung, liver, soft-tissue or bone to qualify for the study (more than one site is permissible)
* At least 1 site of metastasis \>= 20 mm in mean diameter must be identified
* The cancer must over express HER2 as determined by immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH)
* Patients may not have received trastuzumab within 6 weeks of projected 64Cu-DOTA-trastuzumab/PET-CT
* Participants must have normal cardiac ejection fraction
* Ability to provide informed consent
* Patients that may need dose reduction to commence cycle 1 treatment
* Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
* Negative serum pregnancy test (female of childbearing potential only)
* Patients must have adequate cardiac function; left ventricular ejection fraction (LVEF) \>= 50% as determined by multi gated acquisition (MUGA) scan or echocardiogram

Exclusion Criteria:

* Participants who have received trastuzumab within the prior 36 days
* Participants who are not considered candidates for ado-trastuzumab-emtansine
* No metastatic sites \>= 20 mm
* Concurrent malignancy other than skin cancer - Inability to provide informed consent