PS5-10-25: Comparison of survival and recurrence outcomes among breast cancer patients: breast-conserving surgery versus medically necessary and patient preference mastectomy

Abstract Background: Global mastectomy rates for breast cancer have risen over the past decade for unclear reasons. Patients may perceive mastectomy to improve survival and reduce recurrence risk, despite trials showing breast conserving surgery (BCS) with radiation offers equivalent or superior survival in early breast cancer. Although international guidelines support both BCS with radiation and mastectomy for treatment of early breast cancer, emerging evidence favoring BCS challenges the routine practice of offering both equally. Currently, there is no comparative data assessing survival and recurrence outcomes across BCS, medically necessary mastectomy (Mast-MN), and patient preference mastectomy (Mast-PP). This study compared breast cancer-specific survival (BCSS), overall survival (OS), local recurrence (LR), and regional recurrence (RR) between these surgical approaches. Methods: Patients who underwent surgery for stage pT1-3pN0-3 breast cancer at our provincial referral center from 2012-2018 were identified from a prospectively maintained database. Exclusions were for stage 4 disease, synchronous breast cancers, neoadjuvant therapy, or BCS without adjuvant radiation. The indication for mastectomy was coded preoperatively by the consulting surgeon, where a mastectomy was classified as Mast-MN in patients with contraindications to BCS, and Mast-PP for patient preference when BCS was otherwise feasible. To account for our provincial cancer centre’s post-mastectomy radiation guidelines, analyses were stratified by nodal status. BCSS was assessed using a cause-specific hazard model, OS with a Cox proportional hazards model, and LR/RR using a Fine-Gray competing risk model, controlling for age, T stage, receptor status, grade, lymphovascular invasion, adjuvant hormone and chemotherapy, and axillary dissection. Results: Among 1468 node negative patients, 986 underwent BCS, 275 Mast-MN, and 207 Mast-PP. There was no significant difference in BCSS or LR between Mast-PP and BCS, however Mast-PP was associated with significantly worse OS (HR = 2.03, 95% CI: 1.29 -3.20, p=0.02) and greater risk of regional recurrence (SHR = 39.7, 95% CI: 4.95-318, p = 0.001) compared to BCS. Among 628 node positive patients, 354 underwent BCS, 207 Mast-MN, and 67 Mast-PP. There was no significant difference in BCSS, OS, LR, or RR between Mast-PP and BCS in these patients. Conclusions: Mast-PP does not appear to confer any survival or recurrence advantage compared to BCS with radiation. In fact, for node negative patients, Mast-PP may be associated with a higher risk of regional recurrence compared to BCS, due to omission of adjuvant radiation. Citation Format: C. Liu, R. Warburton, C. Dingee, J. Pao, A. Bazzarelli, A. Nichol, E. McKevitt. Comparison of survival and recurrence outcomes among breast cancer patients: breast-conserving surgery versus medically necessary and patient preference mastectomy [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 PS5-10-25.