Prognostic impact of close margins on Loco-regional recurrence in ductal carcinoma in situ treated with breast-conserving surgery and radiotherapy.

INTRODUCTION Current guidelines recommend achieving negative margins ≥2 mm for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery (BCS) and radiotherapy (RT). However, the need for re-excision in cases with close (<2 mm), but negative margins remain controversial. We evaluated the prognostic impact of close margins on locoregional recurrence (LRR) and identified factors associated with recurrence.

MATERIAL AND METHODS We retrospectively analyzed 672 patients with pure DCIS who underwent BCS and adjuvant RT between 2004 and 2020. Patients were categorized into negative- and close-margin groups (n = 611 and 61, respectively). A subgroup analysis was performed on 175 patients with microinvasive carcinoma. Predictors of LRR were assessed using Cox proportional hazards models, and survival outcomes were compared using Kaplan-Meier analysis.

RESULTS During a median follow-up of 88 months, 12 patients (1.8%) developed LRR. In pure DCIS, margin status was not significantly associated with recurrence. Younger age (≤50 years) and omission of hormonal therapy were risk factors for LRR. However, in microinvasive carcinoma, close margins were significantly associated with shorter LRR-free survival. On ultrasonography, lesion size ≥2 cm and non-mass-like appearance were associated with close margin status.

CONCLUSION Close margins were not associated with an increased risk of LRR in pure DCIS patients treated with BCS and RT, suggesting that routine re-excision may be unnecessary. However, in microinvasive carcinoma, close margins were associated with a higher recurrence risk, indicating the need for wider excision. Ultrasonographic features may help to predict close margins and assist in preoperative surgical planning.