Lapatinib in Combination With Vinorelbine

Approximately 105 subjects will be enrolled in the study and randomized 2:1 to one of the following regimens Arm A (n=70): Lapatinib 1250 mg orally once daily continuously plus Vinorelbine 20mg/m2 intravenously (IV) on day 1 and 8, every third week, or Arm B (n=35): Lapatinib 1250 mg orally once daily (QD) continuously plus Capecitabine 2000 mg/m2/day orally in 2 doses 12 hours apart on days 1-14 every third week. Randomization will be stratified according to the following variables: 1) Prior receipt of therapy for metastatic breast cancer (Yes or No), and 2) Site of metastatic disease (Visceral/Soft tissue or Bone-only). Subjects will receive randomized study treatment until disease progression or discontinuation of study treatment due to unacceptable toxicity, withdrawal of consent, lost to follow up, or death. All subjects who discontinue study treatment without documented progression will continue to be followed for progression according to protocol-schedule until new anti-cancer therapy is initiated and/or progression or death is documented. Survival data will be collected for all subjects to ensure a minimum of 18 months survival data. This study will include a safety run-in phase for approximately the first 30 subjects (20 randomized to lapatinib and vinorelbine; 10 to lapatinib and capecitabine).