['metastatic breast cancer']
['paclitaxel', 'eribulin', 'gemcitabine']

        Inclusion Criteria:

          1. Histologically confirmed metastatic, or recurrent breast cancer

          2. HER2-negative breast cancer

          3. age > 18 years

          4. ECOG performance status 0 - 2

          5. Pre- or postmenopausal breast cancer patients with measurable or non-measurable
             lesions, who are candidates for chemotherapy

          6. Life expectancy ≥ 3 months

          7. No prior history of chemotherapy for metastatic, recurrent breast cancer

          8. Patients may have received prior neoadjuvant or adjuvant taxane regimen as long as it
             has been 12 months since completion of regimen.

          9. Patients either may or may not have a prior anthracycline containing regimen.

         10. Prior hormonal therapy as a treatment of metastatic disease is allowed. But
             antitumoral hormonal therapy must be terminated prior to enrollment(up to the date of
             randomization)

         11. Prior radiation therapy allowed as long as < 25% of the bone marrow has been treated,
             and the patients must have recovered from the acute toxic effects of the treatment
             prior to study enrollment. Prior radiation to the whole pelvis is not allowed. Prior
             radiotherapy must be completed 2 weeks before study entry.

         12. Bisphosphonates for the treatment of bone metastases should not be initiated following
             the first dose of randomized therapy. It must be initiated prior to day of treatment
             (cycle 1, day 1). Patients may continue on bisphosphonates who already established on
             bisphosphonate therapy for bone metastases

         13. Adequate bone marrow function (≥ ANC 1,500/ul, ≥ platelet 100,000/ul, ≥ Hemoglobin 9.0
             g/dl)

         14. Adequate renal function (≤ serum creatinine 1.5 mg/dl or CCr ≥ 50 ml/min)

         15. Adequate liver function (≤ serum bilirubin 1.5 mg/dl, ≤ AST & ALTX3 upper normal limit
             or AST and ALT ≤ 5.0XULN if judged by the investigator to be related to liver
             metastases)

         16. Written informed consent

        Exclusion Criteria:

          1. Serious uncontrolled intercurrent infections

          2. Serious intercurrent medical or psychiatric illness, including active cardiac disease

          3. Pregnancy or breast feeding

          4. Second primary malignancy(except in situ carcinoma of the cervix or adequately treated
             nonmelanomatous carcinoma of the skin or other malignancy treated at least 5 years
             previously with no evidence of recurrence)

          5. Documented parenchymal or leptomeningeal brain metastasis

          6. Peripheral neuropathy ≥ grade 2

          7. Prior treatment with gemcitabine will not be allowed.

          8. HER-2 overexpressing breast cancer and concomitant trastuzumab treatment is not
             allowed

          9. Women of childbearing potential, unwilling to use a medically acceptable method of
             contraception during the trial
      