This is a single arm pilot study of 64Cu-MM-302 and unlabeled MM-302 in combination with trastuzumab in 10 patients with advanced HER2+ cancer with new or progressive brain metastases. Patients will receive standard imaging at baseline, including FDG-PET/CT plus MR brain imaging. Patients will subsequently start protocol therapy with MM-302 and trastuzumab given on day 1 of an every 21-day dosing cycle, at the recommended phase 2 dose of 30 mg/m2. Patients will receive 64Cu-labeled MM-302 (3-5 mg/m2 doxorubicin) three hours after unlabeled dose of MM-302. Integrated MR/PET imaging of the brain and whole body will be performed at two time points following 64Cu-labeled MM-302 administration: (1) within 3 hours (+/- 1 hour) of labeled drug injection, and (2) 24 hours (+/- 6 hours) post-injection. Patients will continue to receive subsequent doses of unlabeled MM-302 plus trastuzumab every 3 weeks until clinical or radiographic disease progression (either in the brain or systemically) or unacceptable toxicity, whichever occurs soonest. MR brain imaging and FDG-PET/CT scans will be performed every 9 weeks to monitor for treatment response and disease progression.