Statement: Prior exposure to taxane is obligatory for patients in the primary trial.
Primary_evidence: Inclusion Criteria:   Ability to provide written informed consent   Prior exposure to taxane in the adjuvant, neoadjuvant or metastatic setting   At least one prior regimen of chemotherapy in the setting of metastatic breast cancer; no upper limit on the number of prior endocrine regimens for metastatic breast cancer, however no more than 6 chemotherapeutic regimens may have been given in the metastatic setting   Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2   Patients must have baseline imaging within 30 days prior to the start of therapy and satisfy one of the following:   Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria   At least one non lymph node lesion of >= 1.0 cm or lymph node >= 1.5 cm in short axis by computerized tomography (CT) scan (CT scan thickness no greater than 5 mm which is serially measurable according to RECIST 1.1 using either computerized tomography (CT) or magnetic resonance imaging (MRI)   Lesions that have had radiotherapy must show evidence of progressive disease (PD) based on RECIST 1.1 to be deemed a target lesion   Non-measurable disease by RECIST 1.1 criteria (includes bone only disease and lesions < 10 mm or lymph nodes < 15 mm in short axis) with rising serum CA15-3 or CA 27.29 or CEA documented by two consecutive measurements taken at least 14 days apart with the most recent measurement being within 42 days prior to registration. The second CA 15-3 or CA 27.29 value must have at least a 20% increase over the first and for CA 15-3 or CA27.29 be greater than or equal to 40 units/mL or for CEA be greater than or equal to 4 ng/mL   Absolute neutrophil count >= 1,500/mm^3   Hemoglobin >= 10 g/dL   Platelets >= 100,000/mm^3   Creatinine =< 1.5 x upper limit of normal (ULN)   Total bilirubin =< 1.5 x ULN   Alkaline phosphatase =< 3.0 x ULN; up to 5 x ULN is acceptable if due to bone metastases in the absence of liver metastases   Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) =< 3.0 x institutional upper limit of normal, unless due to liver metastases (=< 5 x ULN)   Women of child-bearing potential (WOCBP) and men must agree to use adequate contraception (hormonal or barrier method of birth control or abstinence) prior to study entry and for the duration of study participation   Life expectancy of > 12 weeks Exclusion Criteria:   Prior treatment with eribulin   Plan to administer any other systemic antitumor including endocrine therapy except for following standard of care treatment:   Trastuzumab at standard dosing human epidermal growth factor receptor 2 (HER2) positive tumors   Denosumab or bisphosphonates to treat metastatic bone disease   Plan to administer concurrent radiation therapy now or for progressive symptoms during treatment   Patients with known central nervous system (CNS) metastases must have stable disease off steroids after treatment with surgery or radiation therapy   Second primary malignancy that is clinically detectable or clinically significant at the time of consideration for study enrollment   Patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic and/or moderate (creatinine clearance [CrCl] 30-50 mL/min) renal impairment   Radiotherapy within 14 days of study treatment   Major surgery within 21 days of study treatment; minor surgery within 2 weeks of study treatment; placement of vascular access device and biopsies allowed and is not considered major or minor surgery   Treatment with any systemic chemotherapy or investigational agents within 3 weeks of the start of study treatment; endocrine treatment must be stopped prior to initiating study treatment; subjects must have recovered from toxicities of prior therapy   Patients with peripheral neuropathy > grade 2 regardless of etiology   Significant cardiovascular impairment: congestive heart failure > class II according to the New York Heart Association (NYHA), unstable angina or myocardial infarction within 6 months of enrollment, or serious cardiac arrhythmia (> grade 2)   Concomitant severe or uncontrolled medical disease   Significant psychiatric or neurologic disorder which would compromise participation in the study   Pregnant or breast-feeding females