Low Dose of Metronomic Cyclophosphamide and Capecitabine in Pretreated HER2-negative Metastatic Breast Cancer

Inclusion Criteria: 1. Females with age between 18 and 80 years old 2. ECOG performance between 0-3 3. Life expectancy more than 3 months 4. Histological proven unresectable recurrent or advanced HER2-negative breast cancer 5. At least one previous therapy regimen (including endocrine therapy) for metastatic breast cancer;suitable for monotherapy (Neoadjuvant or adjuvant docetaxel should be completed at least one year). 6. At least one measurable disease according to the response evaluation criteria in solid tumor (RECIST1.1) 7. No anticancer therapy within 4 weeks 8. Adequate hematologic, hepatic, and renal function,No serious medical history of heart, lung, liver and kidney 9. Provision of written informed consent prior to any study specific procedures 10. Previous capecitabine is permitted, however, it should be completed at least 6 months. Exclusion Criteria: 1. Pregnant or lactating women (female patients of child-bearing potential must have a negative serum pregnancy test within 14 days of first day of drug dosing, or, if positive, a pregnancy ruled out by ultrasound) 2. Women of child-bearing potential, unwilling to use adequate contraceptive protection during the course of the study 3. Treatment with an investigational product within 4 weeks before the first treatment 4. Symptomatic central nervous system metastases 5. Other active malignancies (including other hematologic malignancies) or other malignancies, except for cured nonmelanoma skin cancer or cervical intraepithelial neoplasia. 6. Patient having a history of clinically significant cardiovascular, hepatic, respiratory or renal diseases, clinically significant hematological and endocrinal abnormalities, clinically significant neurological or psychiatric conditions 7. Uncontrolled serious infection 8. Patients with bad compliance 9. Patients lack of Dihydropyrimidine Dehydrogenase(DPD)