The purpose of this study is to assess the efficacy and safety of patients who receive apatinib plus capecitabine or capecitabine for maintenance therapy of patients with with advanced triple-negative breast cancer

Triple-negative breast cancer (TNBC) has the characteristics of early onset, high malignancy, less treatment, and resistance to treatment. Advanced patients have shorter survival than other subtypes. Maintenance therapy after combination chemotherapy can prolong the disease control time in patients with advanced TNBC. How to prolong the disease control time of patients with advanced TNBC without affecting the quality of life has become the focus of current research.

Anti-angiogenic drugs are currently one of the few targeted therapies that have achieved some efficacy in TNBC. Apatinib, a targeted inhibitor of VEGF receptor 2 (VEGFR2), shows significant antitumor activity in the patients with breast cancer. The results of this study will help explore the new treatment of small molecule anti-angiogenic drugs for TNBC maintenance therapy, and provide some new ideas for improving individualized treatment options for patients with advanced TNBC.

Inclusion Criteria:

1. Age：18~75 years;

2. Triple-negative breast cancer (TNBC) confirmed by histology examination;

3. patients had received first-line combination chemotherapy for advanced metastatic disease, and had a complete response, partial response or stable disease according to Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 criteria;

4. received endocrine therapy for metastatic disease before first-line chemotherapy were allowed;

5. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1;

6. A life expectancy of more than 12 weeks;

7. Baseline blood routine examination in accordance with the following criteria : ANC≥1.5×109/L，PLT≥90×109/L，Hb≥90g/L;

8. Liver and renal function in accordance with the following criteria: total bilirubin less than 1.5 times the upper limit of normal value; aspartate aminotransferase (AST), or alanine aminotransferase (ALT) less than 2.5 times the upper limit of normal value, less than 5 times the upper limit of normal value in patients with liver metastases.

   the creatinine clearance rate calculated greater than 60 mL/min;

9. Females of childbearing potential must be a pregnancy test in 7 days before participating ( including serum or urine), and the results were negative, and they are willing to take effective contraceptive methods During the trial and within 8 weeks after the last dose;

10. Obtain informed consent from patients before starting any research-related operations and treatments to confirm that patients are willing to participate in this study and comply with research-related requirements.

Exclusion Criteria:

1. Metastasis/recurrence occurs within 6 months of adjuvant chemotherapy;
2. controlled high blood pressure, systolic blood pressure ≥150mmHg or diastolic blood pressure ≥100mmHg;
3. urine routine test with urinary protein more than ++, or 24 hour urinary protein more than 1.0 g;
4. abnormal coagulation function (INR > 1.5 or prothrombin time (PT) > ULN+4 seconds or APTT >1.5 times the ULN);
5. Pregnant or lactating woman;
6. Symptomatic brain parenchymal and/or pia mater metastases without treatment and control;
7. Patients with Other malignant tumors in the past 5 years, except for fully treated cervical carcinoma in situ, cutaneous squamous cell carcinoma or well-controlled localized basal cell skin cancer;
8. Mental illness or other condition that affects patient compliance;
9. serious and uncontrollable systemic diseases (eg clinically significant cardiovascular disease, lung or metabolic disease, arteriovenous thrombosis, etc.) happened recently;
10. Can not take or absorb oral drugs;
11. Receiving any other testing drugs, or participating in other clinical trial 30 days before being enrolled in this trial;
12. The patient has previously received treatment with an anti-angiogenic drug (whether adjuvant or palliative);
13. Known or suspected to be allergic to any research drug or excipient;
14. Any other researcher believes that it is not appropriate to participate in this test.