The purpose of this prospective observational registry is to monitor safety of eribulin in routine clinical practice. Additionally, this study will also assess the effectiveness of eribulin in real-life settings.

Inclusion Criteria

The participants have to meet all of the following criteria to be eligible to enter into the prospective registry:

1. Participants older than 18 years of age
2. Willing and able to provide informed consent
3. Diagnosis of locally advanced or metastatic breast cancer
4. Progression after up to two previous chemotherapy regimens for advanced disease. Prior therapy should have included an anthracycline and a taxanes in either the adjuvant or advanced setting unless not suitable
5. Adequate bone marrow, liver, and renal function
6. Life expectancy greater than 12 weeks

Exclusion Criteria

Participants meeting the following criteria will not be permitted to enter the study:

1. Prior treatment with eribulin
2. Participants who have received more than two prior chemotherapeutic regimens for advanced disease

Participants with locally advanced or metastatic breast cancer who have progressed after up to two chemotherapeutic regimens for advanced disease will be prospectively included in the registry. Prior therapy should have included an anthracycline and a taxanes unless the patient was not suitable for these treatments.