Eribulin Plus Gemcitabine (EG) vs Paclitaxel Plus Gemcitabine (PG) in HER2-Negative Metastatic Breast Cancer

A total of enrolled 118 patients in EG and PG groups, will be provided chemotherapy regimen: Paclitaxel/Gemcitabine (PG) : every 3 weeks D1 Paclitaxel 175mg/m2 + D5W 500mL MIV over 3hrs before gemcitabine administration D1, D8 Gemcitabine 1,250 mg/m2 + NormalSaline 100ml MIV over 30mins * Pre \& Post medication (which can be changed according to institutions' policy) D1 Corticosteroid 100 mg i.v. 30 min. before Paclitaxel Pheniramine 1A + D5W 50mL MIV 30mins before Paclitaxel Ranitidine 50mg IV + D5W 50mL MIV 30mins before Paclitaxel HT3 antagonist 1A + D5W 50 mL MIV 30mins before Paclitaxel Eribulin/Gemcitabine (EG): every 3weeks D1, D8 Eribulin 1.0 mg/m2, 2-5min iv before gemcitabine (or miv with NormalSaline 100ml in max.) D1, D8 Gemcitabine 1000 mg/m2 + NormalSaline100ml MIV over 30mins \<schedule of Assessment adn procedures (±3 days window period ) \> 1. screening /baseline * obtaining Informed consent form * collecting information * demographic data * breast cancer treatment history/ medical history * general physical examination/ vital sign \& Performance status * Test: CBC/blood chemistry/ Tumor response(CT or MRI)/ * collecting QOL questionnaire using FACT-Taxane 2. cycle 1 \~ prior to EOT * general physical examination/ vital sign \& Performance status * Test: CBC/blood chemistry/ Tumor response(CT or MRI) * collecting QOL questionnaire using FACT-Taxane * administration PG or EG 3. EOT(end of treatment) * general physical examination/ vital sign \& Performance status * Test: CBC/blood chemistry/ Tumor response(CT or MRI) * collecting QOL questionnaire using FACT-Taxane 4. survival follow up(every 12weeks) * survival * anti neoplastic therapy after end of treatment * The tumor response will be performed every 12 (±2) weeks until disease progression \<WITHDRAWAL OF SUBJECTS\> Subjects may be withdrawn from the study (i.e. from any further study medication or study procedure) for the following reasons: * At their own request * If, in the investigator's opinion, continuation in the study would be detrimental to the subject's well-being * In case of disease progression * In case of unacceptable toxicity