TOPLINE

A patient-level analysis found that negative margins < 2 mm after breast-conserving surgery for ductal carcinoma in situ (DCIS) did not increase ipsilateral recurrence risk compared with margins ≥ 2 mm, regardless of radiation receipt, except in women younger than 50 years. Among 11,156 women followed for a median of 66.6 months, only about 4% experienced recurrence, with positive margins being the primary driver of increased risk.

METHODOLOGY

• Current guidelines recommend negative margins of ≥ 2 mm in patients undergoing lumpectomy for DCIS, a threshold based on older, study-level data rather than patient-level evidence. This patient-level analysis of a large, contemporary US cohort evaluated whether negative margins < 2 mm were associated with higher recurrence risk than margins ≥ 2mm.
• The retrospective observational cohort study drew on data from the 2017 Commission on Cancer Special Study, linked to the National Cancer Database. The study included 11,156 women with biopsy-confirmed DCIS (median age at diagnosis, 61 years) who were diagnosed between 2008 and 2015 and had a lumpectomy (breast-conserving surgery) within 6 months of diagnosis.
• Based on final margin width, patients were divided into four groups: positive (tumor on ink), 0.01-0.9 mm, 1.0-1.9 mm, or ≥ 2 mm. Researchers assessed the primary outcome of ipsilateral recurrence, defined as either DCIS or invasive cancer in the same breast.
• Overall, 72.2% (n = 8059) received breast-conserving surgery with radiotherapy, whereas 27.8% (n = 3097) received breast-conserving surgery alone. The median follow-up duration was 66.6 months.

TAKEAWAY

• Overall, recurrence occurred in 4.2% of patients. In multivariable-adjusted analysis among patients who received radiotherapy along with breast-conserving surgery, positive margins increased the risk for recurrence compared with margins ≥ 2 mm (adjusted hazard ratio [aHR], 2.06; P < .001), but margins of 0.01-0.9 mm (aHR, 1.05) and 1.0-1.9 mm (aHR, 1.43) showed no significant difference in recurrence risk compared with margins ≥ 2 mm.
• In multivariable-adjusted analysis among patients who did not receive radiotherapy, positive margins increased recurrence risk compared with margins ≥ 2 mm (aHR, 1.55; P < .05), whereas margins of 0.01-0.9 mm (aHR, 1.37) and 1.0-1.9 mm (aHR, 0.88) showed no significant difference in recurrence risk compared with margins ≥ 2 mm.
• In a subgroup analysis, patients younger than 50 years with negative margins < 2 mm had a significantly higher recurrence risk than those with margins ≥ 2 mm (HR, 1.94).  
• Among patients who received radiotherapy, 5-year recurrence rates were highest (4.4%) with positive margins and lowest (2.0%) with margins ≥ 2 mm, whereas the rates among narrower negative margins fluctuated — 2.3% for 0.01-0.9 mm and 3.4% for 1.0-1.9 mm — showing no consistent trend linking narrower margins to higher recurrence.

IN PRACTICE

"These findings could inform whether re-excision is recommended in patients with close but negative margins, particularly in patients with low clinical risk," the authors wrote.

SOURCE

The study was led by Amanda L. Nash, MD, Duke University Medical Center, Durham, North Carolina. It was published online in the Journal of Clinical Oncology.

LIMITATIONS

The retrospective design left the findings susceptible to unmeasured confounding related to treatment selection. Some subgroup analyses lacked sufficient statistical power because of low recurrence rates. Larger DCIS lesions were also underrepresented, which may have limited generalizability to patients with more extensive disease.

DISCLOSURES

The study was supported by a Patient-Centered Outcomes Research Institute Award and Breast Cancer Research Foundation Awards. Several authors reported consulting fees, research support, or stock ownership involving pharmaceutical and biotechnology companies, including Merck, AstraZeneca, Lilly, and others. Additional author disclosures are reported in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.