This is a randomized clinical trial (OMIT study) evaluating the efficacy of metastasectomy in patients with oligo-metastatic breast cancer.

Inclusion Criteria:

1. women aged 18-70 years old;
2. ECOG score: 0-2 points;
3. the expected life period is more than 3 months;
4. Histologically confirmed metastatic breast cancer: locations include central lung lesions, peripheral lung lesions or liver metastases;
5. PET-CT or other imaging showed patients with ≤3 metastastatic sites, involving 1-2 organs mentioned above, single lesion ≤5cm;
6. according to the RECIST 1.1 edition, there is at least one measurable lesion;
7. the main organs are functioning normally, meeting the following criteria: Blood routine: Hb > 90g/L (no blood transfusion within 14 days); ANC > 1.5 x 109/L; PLT > 75 * 109/L;Liver function: total bilirubin TBIL is less than 1.5 x ULN (upper limit of normal value); ALT and AST are less than 3 x ULN; if there is liver metastasis, ALT and AST are less than 5 x ULN;Renal function: serum creatinine < 1 x ULN;
8. participants voluntarily joined the study, signed informed consent, and followed up.

Exclusion Criteria:

1. the number of metastastatic sites ≥ 3, or the surgeon determines that the R0 resection cannot be achieved;
2. with metastatic lesions other than liver or lung
3. patients with local recurrence
4. palliative radiation therapy or interventional therapy have been performed previously for metastatic lesions
5. has received systemic treatment for metastatic disease, such as chemotherapy, targeted therapy, endocrine therapy, immunotherapy, etc.
6. pregnant or lactating women, women of childbearing age who cannot practice effective contraceptives;
7. involvement in clinical trials of unlisted drugs within 4 weeks before the start of this study;
8. severe cardiopulmonary insufficiency, severe liver and kidney insufficiency;