The purpose of this study is to observe clinical outcomes of metastatic breast cancer patients whose tumors overexpress the Her2neu protein and are being treated with trastuzumab (Herceptin)either alone or combination with chemotherapy or hormonal therapy.

In clinical practice, patients with metastatic breast cancer are being treated either with trastuzumab alone or trastuzumab in combination with chemotherapy or hormonal therapy as it has shown to increase survival. There is currently minimal information as to how long trastuzumab should be given after disease progresses on trastuzumab. This study is a chart review of the above-mentioned population which will capture information such as;

• what chemo or hormonal therapies are chosen by clinicians for Her-2 positive metastatic patients to combine with trastuzumab
• what the number of treatment regimens are (chemo or hormonal) given with trastuzumab
• what the clinical outcome of patients treated is
• what happens to the patients cardiac status with long term administration of trastuzumab
• what treatment patterns exist in the management of central nervous system metastases

This study aims to generate a hypotheses that can be tested from the information collected after is has been analyzed to give clinicians further meaningful data to guide treatment decisions beyond treatment progression.

Inclusion Criteria:

• patients must have metastatic breast cancer
• tumor must have been determined to be Her-2 positive 3+ by immunohistochemistry or gene-amplified by fluorescence-in-situ hybridization (FISH)
• must have received trastuzumab alone or in combination with chemotherapy or hormonal therapy
• must not have received trastuzumab in the adjuvant or neoadjuvant setting
• must have started trastuzumab treatment for metastatic disease any time between January 1996 to June 2003

Exclusion Criteria:

• patients who received trastuzumab prior to 1996

Her-2-neu positive breast cancer patients