Surgery vs. No Surgery for Primary Tumor in De Novo Stage IV Breast Cancer With Solitary Bone Metastases

This is a national multicenter, prospective, randomized controlled trial. The study aims to compare the 5-year overall survival (OS) between patients receiving primary tumor surgery followed by systemic therapy (surgery group) and those receiving systemic therapy alone (non-surgery group) in patients with de novo Stage IV breast cancer who have solitary bone metastases. Secondary objectives include comparing progression-free survival (PFS), breast cancer-specific survival (BCSS), local control rates, patient-reported outcomes (BREAST-Q, QLQ-C30), safety (surgical complications and systemic therapy toxicities), and cost-effectiveness.

Inclusion Criteria: * Female patients aged 18 to 70 years (inclusive); * Histopathologically confirmed (by core needle biopsy) invasive breast cancer; * Diagnosed with de novo Stage IV breast cancer with metastases confirmed to be limited to bone; * Patients may be enrolled either at initial diagnosis or after receiving first-line systemic therapy; * Willing and able to provide written informed consent. Exclusion Criteria: * Disease progression (per RECIST 1.1 criteria) in the primary tumor, regional lymph nodes, or bone metastases after first-line systemic therapy; * Presence of other primary malignancies; * Severe comorbidities that would preclude surgery or safe administration of systemic therapy (e.g., severe cardiopulmonary disease, uncontrolled diabetes, long-term smoking history with poor pulmonary function, immunodeficiency); * Current participation in another clinical trial that would interfere with the outcomes of this study; * Refusal to provide informed consent.