NCT02597868 - 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) | Crick | Crick