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

The value of primary tumor resection in de novo stage IV breast cancer (BC) remains debated. While early retrospective studies suggested a potential survival benefit, recent large-scale randomized controlled trials (e.g., JCOG1017, E2108) have shown no OS benefit for the overall stage IV BC population. However, exploratory subgroup analyses consistently point towards a potential benefit for patients with hormone receptor-positive (HR+) disease and low metastatic burden, such as solitary bone metastases. Given the unique biological behavior of HR+ BC and the effectiveness of modern systemic therapies (e.g., endocrine therapy + CDK4/6 inhibitors), it is hypothesized that primary tumor surgery may provide an additional "consolidation" benefit in this specific subgroup by improving local control and potentially prolonging survival. To address this, our team has designed this national multicenter, prospective, randomized controlled trial. This study will enroll patients with de novo stage IV BC confirmed to have only bone metastases. All participants will receive standard systemic therapy based on their molecular subtype. Participants will be randomized 1:1 to either undergo primary tumor surgery (mastectomy or breast-conserving surgery with or without immediate reconstruction) within 4 weeks of randomization, followed by continued systemic therapy, or to receive systemic therapy alone. Palliative radiotherapy for bone metastases is permitted in both arms. The primary endpoint is 5-year overall survival. Secondary endpoints include PFS, BCSS, local control rate, quality of life (BREAST-Q, QLQ-C30), surgical complication rates, and cost analysis. This study will provide high-level evidence to guide personalized treatment decisions for this specific patient subgroup in China.