MRI-Based Assessment of Margin Status Determinants, Preoperative Predictors, and Prognostic Outcomes in Breast-Conserving Surgery Following Neoadjuvant Therapy.

Background And Purpose: This MRI-based study investigates factors influencing and predictors of margin status in neoadjuvant therapy followed by patients with breast-conserving surgery (NAT-BCS) and evaluates associated locoregional/distant control outcomes.

Materials And Methods: We conducted a retrospective analysis of 117 consecutive patients with breast cancer (BC) who underwent NAT-BCS between June 2014 and June 2024. All patients received magnetic resonance imaging (MRI) examinations both before and after NAT.

Results: Univariate analysis identified factors influencing surgical margin status as molecular subtype (with HER2+ showing the lowest positive rate, followed sequentially by triple-negative breast cancer (TNBC), Luminal B HER2+, Luminal A, and Luminal B HER2-), nonmass enhancement (NME) on pre-NAT MRI, axillary lymph node metastasis, post-NAT MRI shrinkage pattern, postoperative pathological complete response (pCR) status, pN status, and lymphovascular invasion (LVI); however, multivariate analysis demonstrated that only LVI independently affected margin status, and NME on pre-NAT MRI independently predicted margin status, with 106 patients ultimately undergoing BCS, exhibiting a locoregional recurrence (LRR) rate of 1.9% (2/106) and a distant metastasis (DM) rate of 2.8% (3/106).

Conclusion: The presence of NME on pre-NAT MRI could be a predictor for margin status, possibly informing surgical strategy formulation. Concurrently, LVI might represent a distinct determinant influencing margin outcomes. NAT-BCS therapy has achieved favorable local-regional and distant control outcomes.