- HER2 overexpressing breast cancer with at least 1 measurable and no more than 10 unirradiated parenchymal brain metastasis within 21 days prior to study entry
- Newly diagnosed, multiple brain mets
- or Progressive brain mets after stereotactic radiosurgery (SRS) or surgical resection of 1-3 mets
- Karnofsky performance status ≥ 60 within 21 days prior to study entry
- Age ≥ 18
Conditions for Ineligibility
- Prior whole brain radiotherapy (WBRT)
- Prior radiotherapy (any site) with concurrent lapatinib defined as 1 or more days
- Prior invasive malignancy (except non-melanomatous skin cancer, curatively resected thyroid papillary carcinoma, and invasive and non-invasive cancers related to the breast cancer) unless disease free for a minimum of 3 years
- Leptomeningeal disease
- Prior radiotherapy to the region of the study cancer except patients who have progressed following stereotactic radiosurgery for 1-3 brain metastases, with at least one new lesion
Group 1: You will undergo WBRT for 5 days a week for 3 weeks for a total of 15 treatments, or SRS for 1 treatment.
Group 2: You will undergo WBRT or SRS as in group 1. You will also receive lapatinib ditosylate for 6 weeks.