GW572016 In Patients With Advanced Or Metastatic Breast Cancer

Inclusion Criteria: * Confirmed advanced (IIIb or Stage IV) breast cancer who have progressed on prior anthracycline and taxanes containing regimens + trastuzumab for cohort A patients. * Patients must have adequate blood, liver, and kidney function and either be fully active or restricted only in performing strenuous activity. * Female patients of child-bearing potential must be willing to abstain from intercourse from 2 weeks prior to administration of the first dose of study medication until 28 days after the final dose of study medication or be willing to consistently and correctly use an acceptable method of birth control. Exclusion Criteria: * Patients with certain heart problems.