A 2-mm margin should be the standard margin for breast-conserving surgery for patients with ductal carcinoma in situ (DCIS) also receiving whole breast irradiation (WBRT), according to a new consensus guideline released by the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Surgical Oncology (SSO).1

A multidisciplinary consensus panel determined that negative margins reduce the risk of ipsilateral breast tumor recurrence (IBTR) by half, in contrast with positive margins, defined as ink on DCIS.

The panel also found that a 2-mm margin minimizes the risk of IBTR versus negative margins smaller than 2 mm, and more widely clear margins do not significantly improve IBTR compared with 2 mm margins.

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Negative margins less than 2 mm alone are not an indication for mastectomy, and factors associated with IBTR rates should be considered when determining if re-excision is necessary.

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The panel’s recommendations are based on a meta-analysis of margin width and IBTR from a systemic review of 20 studies that included 7883 patients and other literature.                


  1. Morrow M, Van Zee KJ, Solin LJ, et al. Society of Surgical Oncology–American Society for Radiation Oncology–American Society of Clinical Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in ductal carcinoma in situ. J Clin Oncol. 2016 Aug 15. doi: 10.1200/JCO.2016.68.3573 [Epub ahead of print]