Margins in Breast-Conserving Surgery After Neoadjuvant Therapy.

BACKGROUND: Optimal margin width for breast-conserving therapy (BCT) after neoadjuvant chemotherapy (NAC) is unknown. We sought to determine the impact of margin width on local recurrence and survival after NAC and BCT.

METHODS: Patients treated with NAC and BCT for stage I-III breast cancer from 2002 to 2014 were identified. Multivariate Cox regression was performed to determine the relationship between margin width and local recurrence free-survival (LRFS), disease-free survival (DFS), and overall survival (OS).

RESULTS: A total of 382 patients were included. Median age was 51 years [range 22-79], median tumor size 3.0 cm [range 0.6-11.0], and receptor subtypes included 144 (37.7%) HR-/HER2-, 47 (12.3%) HR-/HER2+, 118 (30.9%) HR+/HER2-, and 70 (18.3%) HR+/HER2+. Breast pathologic complete response (pCR) was achieved in 105 (27.5%) patients. Final margin status was positive in 8 (2.1%) patients, ≤ 1 mm in 65 (17.0%), 1.1-2 mm in 30 (7.9%), and > 2 mm in 174 (45.5%). The 5-year LRFS was 96.3% (95% CI 94.0-98.6), DFS was 85.5% (95% CI 81.8-90.7), and OS was 90.8% (95% CI 87.4-94.2). There was no difference in LRFS, DFS, or OS for margins ≤ 2 versus > 2 mm, and no difference in DFS or OS for margins ≤ 1 versus > 1 mm. HR+ subtype (p = 0.04) and pCR (p = 0.03) were correlated with favorable DFS and node negativity (p < 0.001) with favorable DFS and OS.

CONCLUSIONS: In this cohort treated with NAC and BCT, there was no association between margin width and LRFS, DFS, or OS. Although further studies are needed, the excellent long-term outcomes demonstrated in patients with close (≤ 2 mm) margins following NAC suggest that a margin of "no-ink-on-tumor" may be acceptable in appropriately selected patients.