Abstract Background: Breast cancer treatment increasingly incorporates breast-conserving approaches that integrate oncologic control with superior cosmetic outcomes. Among these, oncoplastic breast-conserving surgery (OBS), such as therapeutic mammoplasty, has gained popularity, particularly in patients with larger tumors or moderate-to-large breasts. However, robust comparative data on its oncologic safety versus standard breast-conserving surgery (BCS) remain limited, especially in low- and middle-income countries like Brazil. This multicenter cohort study aimed to compare recurrence-free survival (RFS), locoregional recurrence-free survival (LRRFS), breast cancer-specific survival (BCSS), progression-free survival (PFS), and overall survival (OS) between patients undergoing therapeutic mammoplasty and BCS. Methods: A retrospective cohort study was conducted across six Brazilian institutions (five private and one public hospital). Eligible patients were women aged 18 years or older with clinical stage 0-III breast cancer who underwent either BCS or therapeutic mammoplasty between 2016 and 2022. Data collected included demographics, tumor and treatment characteristics, and type of surgical approach. Kaplan-Meier analysis was used to estimate survival outcomes, and Cox proportional hazards models were employed to identify independent predictors of recurrence and survival. Logistic regression analysis evaluated factors associated with surgical technique selection. The study was approved by the institutional ethics committee (IDOR reference 6,907,736). Results: A total of 685 patients were included, of whom 550 (80.3%) underwent BCS and 135 (19.7%) underwent therapeutic mammoplasty. Patients who underwent therapeutic mammoplasty were significantly younger (mean age 53.3 vs. 59.5 years) and had more advanced tumor characteristics, including higher clinical T-stage (T2: 36.3% vs. 24.5%; T3: 8.1% vs. 2.5%) and greater frequency of stage IIB or higher (24.8% vs. 10.8%). Multivariate analysis showed that higher tumor stage (OR=2.71; p=0.001) and treatment in public hospitals (OR=0.41; p=0.001) were independent predictors for receiving therapeutic mammoplasty. Despite these baseline differences, survival outcomes were similar between groups. No statistically significant differences were observed for RFS (HR=0.36; p=0.091), LRRFS (HR=0.35; p=0.085), BCSS (HR=0.36; p=0.091), PFS (HR=0.52; p=0.169), or OS (HR=0.53; p=0.314). Five-year RFS rates were excellent in both groups (97.3% for therapeutic mammoplasty vs. 96.0% for BCS), as were LRRFS rates (96.6% vs. 92.2%). Positive surgical margin rates were low overall (1.5% for therapeutic mammoplasty and 4.2% for BCS), likely due to careful surgical planning, intraoperative frozen section, and larger volume resections in oncoplastic procedures. Conclusion: In this large Brazilian multicenter cohort, therapeutic mammoplasty demonstrated oncologic safety equivalent to standard breast-conserving surgery, even in patients with more advanced tumors. These results support the integration of oncoplastic techniques in breast cancer surgical care, particularly when individualized according to tumor characteristics, patient anatomy, and healthcare setting. While short- to medium-term outcomes are reassuring, prospective studies with longer follow-up are warranted to further validate the oncologic equivalence of therapeutic mammoplasty. Citation Format: A. Dominique Nascimento Lima, F. Pimentel Cavalcante, A. Mattar, F. Pereira Zerwes, M. Antonini, M. Leite Kraft, A. Oliveira de Alencar, A. de Queiroz Germano, D. Pitanga Torres, E. Goulart Carneiro, C. Freitas de Lima, R. Zocchio Torresan, F. Palermo Brenelli, M. Lichtenfels, A. Frasson, J. Bines, E. Camargo Millen. Survival outcomes after lumpectomy versus therapeutic mammoplasty in breast cancer patients: a Brazilian cohort study abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-03-08.
Lima et al. (Tue,) studied this question.