• Patients provided written informed consent

• Women aged 18-75 years old

• Histologically confirmed breast cancer and after radical mastectomy

• Patients of breast cancer with ipsilateral humerus or sternum oligometastasis, and there is no imaging evidence of other site metastases

• Patients must have recovered to baseline condition or to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 grade = 1 from any acute CTCAE v. 5.0 grade =2 side effects of previous treatments

• Without infection of human immunodeficiency virus (HIV) on central laboratory assay results prior to randomization

• Alanine aminotransferase (ALT) \</= 2.5 × the upper limit of normal (ULN), Aspartate aminotransferase (AST) \</= 2.5 × ULN prior to randomization

• Total bilirubin (TBIL) \</= 1.25 × ULN

• Alkaline phosphatase (ALK) \</= 2.5 × ULN

• Gamma glutamyl transpeptidase (GGT) \</= 2.5 × ULN

• Albumin \>/= 30g/L

• Eastern Cooperative Oncology Group (ECOG) performance score of 0 to 2

• Women of child-bearing age should take effective contraceptive measures

• Serum total bilirubin (TBil) \</= 1.5 × ULN

• Serum creatinine (Scr) \</= 1.5 × ULN

• White blood cell count (WBC) \>/= 3×109/L, Blood neutrophil count \>/= 1.5×109/L, Platelet count \>/= 100×109/L, Hemoglobin (HB) \>/= 9 g/dL