Oncological outcomes of breast-conserving surgery versus mastectomy following neoadjuvant chemotherapy in a contemporary multicenter cohort.

To evaluate local recurrence (LR), distant recurrence (DR) and death in non-metastatic patients undergoing breast-conserving surgery (BCS) or mastectomy following current neoadjuvant chemotherapy (NAC) regimens. Patients submitted to NAC in 2013-2023 were evaluated (n = 365; mastectomy: 165; BCS: 200). More mastectomy patients were over 70 years old (12.7% versus 7%; p = 0.02) and had T4b tumors (16.4% versus 4.5%; p = 0.0003), whereas more BCS patients had node-negative axilla (42% versus 31.5%; p = 0.02). After a mean follow-up of 65 months (range: 4-124), LR and DR were similar in the mastectomy and BCS groups (4.8% versus 5.0%; p = 0.95 and 10.9% versus 9%; p = 0.58, respectively). More deaths occurred in the mastectomy group (8.5% versus 3%; p = 0.03). Ten-year LR-free survival was higher in the BCS group (98.5% versus 95%; HR: 3.41; 1.09-10.64; p = 0.03), while 10-year DR-free survival was similar in both groups (91% BCS versus 89% mastectomy, HR: 1.25; 0.65-2.42; p = 0.4). Overall survival was better in the BCS group (97% versus 91.5%; HR: 2.62; 1.06-6.69; p = 0.03). Estimated 10-year disease-free survival, stratified according to tumor stage, showed no significant difference except for T4 disease, for which the risk was greater in the mastectomy group (94.5% versus 81.8%; HR: 2.86, 1.54-5.30, p = 0.0008). In the multivariate analysis, T3/T4 staging (OR: 4.37, 1.03-21.91; p = 0.04) and axillary dissection (OR: 5.11, 1.14-35.52; p = 0.04) were associated with LR in the BCS group. In this cohort of patients receiving contemporary NAC, BCS proved to be a safe alternative to mastectomy following treatment with NAC, even in cases of locally advanced BC.