This is a randomized, multi-center, multinational, open-label, active-controlled, parallel design study of the combination of neratinib plus capecitabine versus the combination of lapatinib plus capecitabine in HER2+ MBC patients who have received two or more prior HER2 directed regimens in the metastatic setting. Patients will be randomized in a 1:1 ratio to one of the following treatment arms:
* Arm A: neratinib (240 mg once daily) + capecitabine (1500 mg/m\^2 daily, 750 mg/m\^2 twice daily \[BID\])
* Arm B: lapatinib (1250 mg once daily) + capecitabine (2000 mg/m\^2 daily, 1000 mg/m\^2 BID)
Patients will receive either neratinib plus capecitabine combination or lapatinib plus capecitabine combination until the occurrence of death, disease progression, unacceptable toxicity, or other specified withdrawal criterion.
