Narrow DCIS Margins May Not Always Warrant Reexcision

An ancillary analysis found less than 2-percentage-point differences in 10-year recurrence across margin thresholds, with no statistically significant adjusted association.

By
Andrea Surnit
July 20, 2026
6 min

Conexiant

Overview

This study evaluates the association between lumpectomy margin width and ipsilateral breast tumor recurrence (IBTR) in postmenopausal patients with hormone receptor-positive ductal carcinoma in situ (DCIS). Findings indicate that margin width was not significantly associated with recurrence after adjustment for confounding factors.

Background

The management of ductal carcinoma in situ (DCIS) often involves breast-conserving surgery, and the width of surgical margins has been a critical factor in determining the need for reexcision. Current guidelines recommend a 2-mm negative margin; however, the necessity of this threshold has been questioned based on new evidence suggesting that narrower margins may not significantly impact recurrence rates.

Data Highlights

Margin Width	IBTR Events	10-Year Cumulative Incidence
< 1 mm	24 of 502	5.6%
>= 1 mm	66 of 2,205	4.0%
< 2 mm	39 of 879	5.3%
>= 2 mm	49 of 1,667	3.8%

Key Findings

Narrower margins (less than 1 mm) were associated with a 10-year IBTR rate of 5.6% compared to 4.0% for margins of at least 1 mm.
After adjusting for age, endocrine therapy assignment, and tumor size, margin width was not significantly associated with IBTR.
Approximately one-third of ipsilateral recurrences were invasive.
10-year cumulative incidence of all breast cancer events was 9.5% for margins less than 1 mm and 8.5% for margins at least 1 mm.
65% of patients completed 5 years of endocrine therapy, with no difference in adherence by margin group.