For a patient to be eligible for participation in this study, all of the following criteria must apply.
- Pathologically (histologically or cytologically) proven diagnosis of invasive breast cancer
- HER2-overexpressing breast cancer (3+ staining by immunohistochemistry or HER2 gene amplification by fluorescent in situ hybridization [FISH] or silver in situ hybridization [SISH] >= 2.0)
- At least 1 measurable unirradiated parenchymal brain metastasis within 21 days prior to study entry; patients who are to undergo SRS must have no more than 10 brain metastases; there is no limit on number of brain metastases for WBRT; the minimum size as measured on T1-weighted gadolinium-enhanced MRI must be as follows according to the number of brain metastases:
- For a single solitary lesion the size must be >= 10 mm
- For 2 or more lesions, the size of at least 2 of the lesions must be >= 5 mm
Patients may also have the following provided the size requirements above are met:
- Progressive parenchymal brain metastasis following stereotactic radiosurgery for 1-3 brain metastases, with at least 1 new measurable brain lesion
- Progressive parenchymal brain metastasis following surgical resection of 1-3 brain metastases, with at least 1 measurable brain lesion
- History/physical examination within 21 days prior to study entry
- Karnofsky performance status >= 60 within 21 days prior to study entry
- Able to swallow and retain oral medication (note: for patients unable to swallow tablets, an oral suspension preparation is acceptable)
- Absolute neutrophil count (ANC) >= 1,200 cells/mm^3, within 21 days prior to study entry
- Platelets >= 70,000 cells/mm^3, within 21 days prior to study entry
- Hemoglobin >= 8.0 g/dL (note: the use of transfusion or other intervention to achieve hemoglobin [Hgb] >= 8.0 g/dL is acceptable), within 21 days prior to study entry
- Creatinine < 1.5 times institutional upper limit of normal, within 21 days prior to study entry
- Bilirubin < 1.5 times institutional upper limit of normal, within 21 days prior to study entry
- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) =< 3.0 times institutional upper limit of normal with or without liver metastasis, within 21 days prior to study entry
- Patient must provide study specific informed consent prior to study entry
- Women of childbearing potential must have a negative serum pregnancy test within 21 days prior to study entry
- Sexually active women of childbearing potential and sexually active men must practice adequate contraception during therapy and for 12 months after protocol treatment completion
- Prior lapatinib is allowed as long as the last dose received was > 21 days prior to study entry and provided the patient has not received it at any time after the diagnosis of brain metastasis