De-Escalation Surgery in cT3-4 Breast Cancer Patients after Neoadjuvant Therapy: Predictors of Breast Conservation and Comparison of Long-Term Oncological Outcomes with Mastectomy

Simple Summary Neoadjuvant therapy (NAT) has transformed the treatment of advanced breast cancer (BC), making previously inoperable tumors operable and allowing for the direct observation of treatment response. This approach reduces the need for extensive surgery, making breast-conserving surgery (BCS) a viable option for more patients. Despite the shift towards less-invasive surgery, the decision between BCS and mastectomy remains complex, influenced by numerous factors. Our study specifically looked at patients with cT3-4 BC treated with NAT, aiming to identify independent factors that predict the likelihood of undergoing BCS and to compare long-term oncological outcomes between BCS and mastectomy. We found that the absence of vascular invasion, smaller tumor size post-NAT, and achieving a complete response of the primary tumor were key predictors for breast conservation. Our results indicate that BCS post-NAT does not negatively impact long-term oncological outcomes, supporting its use as a safe option for patients with cT3-4 BC.Abstract Background: Neoadjuvant therapy (NAT) has become increasingly employed for the treatment of cT3-4 breast cancer (BC), enabling breast-conserving surgery (BCS) in cases traditionally considered for mastectomy. This study aims to identify predictors for breast conservation post-NAT and to evaluate whether BCS influences long-term oncological outcomes. Methods: We retrospectively analyzed data from patients with cT3-4 BC who received NAT at the Breast Unit of IRCCS Humanitas Research Hospital, Milan, Italy, from October 2009 to April 2020. Surgical outcomes and long-term oncological results, such as disease-free survival (DFS), distant DFS (DDFS), overall survival (OS), and BC-specific survival (BCSS), were compared between the BCS and mastectomy groups. Results: Among 114 patients analyzed, 37 (32.5%) underwent BCS, and 77 (67.5%) had a mastectomy. The key predictors for opting for BCS included absence of vascular invasion, reduced tumor size post-NAT, and achieving ypT0 status. No significant differences in DFS, DDFS, OS, and BCSS were observed between the two surgical groups (log-ranks, p = 0.520, p = 0.789, p = 0.216, p = 0.559, respectively). Conclusions: BCS after NAT is a feasible and safe option for patients with cT3-4 BC, without adversely affecting long-term oncological outcomes. Identifying predictors of breast conservation can guide surgical decision-making, ensuring that patients receive optimal treatment.