Xiao-Wen Lan,1,2,* Ge Wen,3,* Zhen He,4 Jiang-Hua Huang,1,2 Xue-Bin Zou,5 Xiao Lin,1,6 Yu-Ting Tan,1,6 Xiao-Bo Huang1–2,61Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, People’s Republic of China; 2Department of Radiation Oncology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, People’s Republic of China; 3Department of Radiation Oncology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, People’s Republic of China; 4Department of Oncology, The First Affiliation Hospital of Guangdong Pharmaceutical University, Guangzhou 510062, People’s Republic of China; 5Department of Ultrasound, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangdong 510060, People’s Republic of China; 6Department of Breast Tumor Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510120, People’s Republic of China*These authors contributed equally to this workPurpose: Postoperative radiotherapy (RT) can improve survival for T1-2N1 breast cancer. However, there exists a concern whether BCS plus RT has the same or a superior therapeutic effect as that of mastectomy. In this study, we aimed to compare the long-term results between RT after BCS and postmastectomy RT in stage T1-2N1M0 breast cancer.Patients and Methods: Totally 1816 pathological stage T1-2N1M0 breast cancer patients were analyzed. The propensity score matching (PSM) method was used to select 196 pairs of patients between BCS and mastectomy receiving postoperative RT. Five-year locoregional relapse (LRR), locoregional relapse-free survival (LRFS), distant metastasis (DM), distant metastasis-free survival (DMFS), disease-free survival (DFS), breast cancer-specific survival (BCSS) were analyzed as endpoints.Results: In the whole group, significant differences were observed in all endpoints (P