Irinotecan/Capecitabine Versus Capecitabine in Patients Treated With A/T for HER2 Negative Metastatic Breast Cancer

Inclusion Criteria: * Histologically confirmed stage IV or recurrent breast cancer * HER2 negative disease, or HER2 unknown disease not eligible for anti-HER2 therapy * ECOG performance status 0-2 * Age ≥ 20 years * Patients who received anthracycline based chemotherapy in the (neo)adjuvant or metastatic setting and experienced disease progression on taxane based chemotherapy in the metastatic setting, or patients who experienced disease recurrence within 1 year after completion of (neo)adjuvant anthracycline and taxane based chemotherapy * In case of patients treated with capecitabine in an adjuvant setting, disease recurrence should not be occurred within 1 year after completion of capecitabine chemotherapy * Patients with brain metastasis can be enrolled when they don't need any treatment regarding to brain metastasis * Previous any chemotherapy and radiotherapy should be completed at least 3 weeks before randomization- Measurable or evaluable disease according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 \[21\] * Adequate hematopoietic function: absolute granulocyte count ≥ 1,500/mm3, platelet ≥ 100,000/mm3, hemoglobin ≥ 10g/mm3 * Adequate hepatic function: total bilirubin ≤ 1.5mg/dL, alkaline phosphatase(ALP) ≤ 2.5 x UNL, AST/ALT ≤ 2x UNL, or if liver function abnormalities due to underlying malignancy exists, AST/ALT ≤ 2.5 x UNL, total bilirubin ≤ 3.0mg/dL, (ALP) ≤ 5 x UNL in cases with bone metastasis; ALP ≤ 5 x UNL * Adequate renal function : serum creatinine ≤ 1.5mg/dL * Ability to understand and comply with protocol during study period * Patients should sign a written informed consent before study entry Exclusion Criteria: * Pregnant or lactating women * Patients who receive irinotecan or capecitabine for metastatic breast cancer treatment * Patients with HER2 positive breast cancer * Grade 2 or greater peripheral neuropathy * Patients with symptomatic brain metastasis * Prior unanticipated severe reaction to fluropyrimidine therapy or known sensitivity to 5-fluorouracil * Patients who have history of cancer other than in situ cervical cancer or non-melanotic skin cancer * Patients with GI tract disease resulting in an inability to take oral medication, malabsorption syndrome, a requirement for IV alimentation, prior surgical procedure affecting absorption, uncontrolled GI disease (e.g. Crohn's disease, ulcerative colitis)