A Multicenter, Randomized Clinical Trail Evaluate Effectiveness and Security of Capecitabine or Endocrinotherapy as a Maintenance Therapy Regimen After the 1st-line Chemotherapy With Capecitabine Combine Regimen in Hormone Receptor Positive and HER2 Negative Metastatic Breast Cancer(Overstep)

Inclusion Criteria

• •Signed informed consent
• •The age is Above 18 years of age, \<70 years old
• •HR-positive \& HER2-negative
• •Metastatic breast cancer,incurable.
• •No prior chemotherapy for metastatic recurrence, if there is disease progression within 6 months after the end of the adjuvant chemotherapy, adjuvant chemotherapy as first-line treatment for metastatic lesions
• •Eastern Cooperative Oncology Group performance status (ECOG PS)=0\~1
• •The basic function of normal bone marrow
• •Functions of liver and kidney is normal
• •Expectation of life is more than 3 months
• •Agreed to take contraceptive measures during treatment