GW572016 For Treatment Of Refractory Metastatic Breast Cancer

Inclusion Criteria:

* Signed Informed Consent.
* Histologically confirmed Stage IIIb or IV breast cancer.
* Refractory breast cancer defined as progression in the metastatic setting after prior therapy with anthracyclines, taxanes and capecitibine.
* Subjects with documented ErbB2 tumor overexpression must have received at least 6 cycles of trastuzumab.
* Documented disease progression of the most recent treatment is required.
* Archived tumor tissue available for testing.
* Measurable lesions according to Response Evaluation Criteria In Solid Tumors (RECIST).
* At least 3 weeks since prior cancer therapies except for trastuzumab which must be discontinued at least 2 weeks prior to the beginning of study drug.
* Bisphosphonate therapy initiated prior to study entry is allowed, however, initiation of bisphosphonates following study entry is not allowed.
* Able to swallow and retain oral medication.
* Cardiac ejection fraction within the institutional normal range as measured by echocardiogram or MUGA (Multiple Gated Acquisition) scan.
* Adequate kidney and liver function.
* Adequate bone marrow function.

Exclusion criteria:

* Pregnant or lactating.
* Copies of nadir scans and/or photographs of the tumor prior to disease progression as well as scans documenting disease progression are not available for review.
* Malabsorption syndrome, ulcerative colitis, disease significantly affecting gastrointestinal function or resection of the stomach or small bowel.
* History of other malignancy.
* Serious medical or psychiatric disorder that would interfere with the patient''s safety or informed consent.
* Active or uncontrolled infection.
* Known history of uncontrolled or symptomatic angina, arrhythmias or congestive heart failure.
* Known history of or clinical evidence of leptomeningeal carcinomatosis.
* Active infection.
* Concurrent cancer therapy or investigational therapy.
* Use of oral or IV steroids.
* Unresolved or unstable serious toxicity from prior therapy.
* Prior treatment with an ErbB1 and/or ERbB2 inhibitor other than trastuzumab.