To evaluate and compare the outcomes of supraclavicular lymph node dissection plus radiotherapy (RT) and RT alone for patients with synchronous ipsilateral supraclavicular lymph node metastasis.In all, 293 patients with synchronous ipsilateral supraclavicular lymph node metastasis across three centers were included. Of these, 85 (29.0%) received supraclavicular lymph node dissection plus RT (Surgery + RT) and 208 (71.0%) received RT alone. All patients received preoperative systemic therapy followed by mastectomy or lumpectomy and axillary dissection. Supraclavicular recurrence-free survival (SCRFS), locoregional recurrence-free survival (LRRFS), distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS) were evaluated by using the Kaplan-Meier method and multivariate Cox models. Multiple imputation was used for missing data.The median follow-up duration of the RT and Surgery + RT groups were 53.7 and 63.5 months, respectively. For the RT and Surgery + RT groups, the 5-year SCRFS rates were 91.7% vs. 85.5% (P = 0.522), LRRFS rates were 79.1% vs. 73.1% (P = 0.412), DMFS rates were 60.4 vs. 58.8% (P = 0.708), DFS rates were 57.6% vs. 49.7% (P = 0.291), and OS rates were 71.9% vs. 62.2% (P = 0.272), respectively. There was no significant effect on any outcome when comparing Surgery + RT versus RT alone in the multivariate analysis. Based on four risk factors of DFS, patients were classified into three risk groups: the intermediate- and high-risk groups had significantly lower survival outcomes than the low-risk group. Surgery + RT did not improve outcomes of any risk group compared with RT alone.Patients with synchronous ipsilateral supraclavicular lymph node metastasis may not benefit from supraclavicular lymph node dissection. Distant metastasis remained the major failure pattern, especially for intermediate- and high-risk groups.Copyright © 2023 Elsevier B.V. All rights reserved.