Inclusion Criteria

Inclusion criteria:

- Histologically confirmed invasive breast cancer with incurable stage IIIB, IIIC with
T4 lesion or stage IV disease at primary diagnosis or at relapse after curative
intent surgery.

- Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.

- Documented amplification of ErbB2 by Fluorescence in situ hybridization (FISH)

- Measurable disease by Response Evaluation Criteria In Solid Tumors (RECIST)

- Adequate renal, hepatic and cardiac function

Exclusion criteria:

- Prior chemotherapy, immunotherapy, biologic therapy or anti-ErbB1/ErbB2 therapy other
than adjuvant therapy. [Prior neo-adjuvant or adjuvant therapy (including
trastuzumab) will be allowed provided it was stopped at least 12 months before study
entry.

- Patients with active brain metastases

- Patients with bilateral breast cancer, bone metastases as the only disease site or
metastases to more than 30% of the hepatic parenchyma.