Survival outcomes after standard breast conserving surgery versus oncoplastic breast conserving surgery in breast cancer patients: A multicenter real-world evidence cohort study

Background Standard breast-conserving surgery (S-BCS) followed by radiotherapy is the preferred locoregional treatment for early-stage breast cancer but may result in unfavorable cosmetic outcomes, particularly in patients with small breasts. Oncoplastic breast-conserving surgery (O-BCS), allows wider resections while preserving breast shape. Although esthetic benefits are well established, data comparing long-term oncologic outcomes remain limited. Objective To compare oncologic outcomes between O-BCS and S-BCS in a multicenter real-world cohort. Methods This multicenter retrospective cohort study included women aged ≥ 18 years with stage 0–III breast cancer who underwent BCS followed by adjuvant radiotherapy between 2016 and 2022 at six institutions in Brazil. Survival outcomes were estimated using Kaplan–Meier methods and compared using multivariable Cox proportional hazards models adjusted for clinical stage. Results A total of 685 patients were included, of whom 550 (80.3%) underwent S-BCS and 135 (19.7%) O-BCS. Patients treated with O-BCS more frequently presented with advanced disease (≥IIB: 24.8% vs. 10.8%; p < 0.001). No statistically significant differences in survival outcomes were observed. At 60 months, LRRFS was 90.0% for S-BCS and 96.3% for O-BCS (HR 0.35; p = 0.085), RFS was 89.7% and 96.1%(HR 0.36; p = 0.091), BCSS was 97.3% and 98% (HR 0.26; p = 0.198), and OS 96% and 97.3% (HR 0.53; p = 0.31) respectively. Conclusion In this multicenter real-world cohort, O_BCS achieved oncologic outcomes comparable to S-BCS despite being used in patients with more advanced disease, supporting its use as a breast-conserving strategy in appropriately selected patients.