ASCO Issues Guideline on Margins for Breast-conserving Surgery in DCIS


A new guideline on margins for breast-conserving surgery was released this month.

For patients with DCIS (ductal carcinoma in situ) who are also receiving whole breast irradiation (WBRT), a 2-mm margin should be the standard margin. The guideline was released by the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Surgical Oncology (SSO).

This significant news was determined by a multidisciplinary consensus panel which found that negative margins reduce the risk of IBTR (ipsilateral breast tumor recurrence) by half, as opposed to positive margins, defined as ink on DCIS. They also found that a 2-mm margin minimizes the risk of IBTR versus negative margins less than 2 mm, and that more widely clear margins do not significantly improve IBTR compared to 2-mm margins.

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

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


  • 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]