Abstract PS2-01-03: Is Breast Conserving Surgery a Viable Option for Non-Inflammatory T3/T4 Breast Cancer?

Abstract Background: Breast conserving surgery for locally advanced breast cancer remains a controversial approach,Historically mastectomy has been the preferred surgical intervention for patients with T3/T4 breast cancer. However,the utilization of neoadjuvant systemic therapy (NAST), development of oncoplastic breast conserving techniques rendered BCS an increasingly appealing option for patients and surgeons. Methodology: Study aims to evaluate the surgical and oncological safety of BCS for non-inflammatory, non-multicentric T3/T4 non-metastatic breast cancer through a retrospective analysis of prospectively maintained data. 75 female patients diagnosed between 2017 and 2024. Analysis encompassed clinico-pathological characteristics, treatment modalities and surgical outcomes, including surgical margins, rates of margin re-excision and conversion to mastectomy and pathologic complete response (PCR) or down-staging to a lower tumor stage after NAST. Oncological outcomes included disease recurrence and overall survival. Result: Out of 75 patients, 43 (57%) had T3 lesion,32 (43%) had a T4a-c lesion. Mean age of patients was 52 years. Most of patients had an invasive ductal histology (95%) of high grade (71%), node positive (60%). Luminal type comprised 41%,37% triple negative and 21% were HER2neu positive. BCS associated with positive surgical margins in 2 patients (2.6%) one underwent margin re-excision (1.3%), other patient (1.3%) converted to mastectomy for margin clearance. Most of the patients received NAST; 63 (84%) chemotherapy, 6 (8%) hormonal therapy. Majority (93%) received adjuvant radiotherapy. PCR observed in 31(45%) patients,35 (50%) achieved down-staging to smaller tumor size, including patients with triple negative or HER2 positive. 3 patients (5%) with luminal type failed to achieve pathological response to NAST and had identical clinical and pathological tumor stages. On multivariate analysis, patients with TN (70%) and HER2 positive (50%) were likely to achieve PCR after NAST, compared to patients with luminal type (8%) (P0.001). with average follow up duration of 34 months, our cohort demonstrated an overall survival rate of 95%. While the majority of patients remained disease-free, Tumor recurrence was observed in 10 (13%) patients. No isolated local recurrences. Most recurrences were systemic (11%), compared to one systemic and local, and another Locoregional recurrence (1% each). Systemic recurrences were predominantly associated with HER2 positive (50%) grade 3 (60%) and characterized by the lack of PCR (78%) after NAST. However, this did not correlate to statistical significance. Discussion: Data demonstrates that BCS for T3/T4 non inflammatory breast cancer after NAST is associated with low rates of positive surgical margins and conversion to mastectomy, while maintaining acceptable outcomes after oncoplastic surgery, including level 1 and 2, therapeutic reduction mammoplasty, and chest wall perforator flap reconstruction. Isolated local recurrence was rare, and most recurrences were systemic, suggesting that treatment failure was primarily systemic rather than regional. Interestingly, the two patients who experienced local recurrence had negative surgical margins following BCS; however, they did not receive adjuvant radiation, and both had a triple positive, the association between local recurrence and HER2-positive subtype, high tumor grade, and lack of PCR highlights the impact of tumor biology on prognosis Conclusion: BCS for non-inflammatory T3/T4 breast cancer appears to be both surgically and oncologically safe after NAST. Therefore, it should be considered and thoroughly discussed with the patient as a viable treatment alternative to mastectomy. Citation Format: L. Almaghrabi, J. Alazhri, F. Aldulaijan, N. Almana, S. Alajmi, M. Alduhaileb, A. Abbas. Is Breast Conserving Surgery a Viable Option for Non-Inflammatory T3/T4 Breast Cancer? 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 PS2-01-03.