Morrow, MonicaVan Zee, Kimberly J.Solin, Lawrence J.Houssami, NehmatChavez-MacGregor, MarianaHarris, JayHorton, JanetHwang, ShelleyJohnson, Peggy L.Marinovich, M. LukeSchnitt, StuartWapnir, IreneMoran, Meena S.2016-11-182016Morrow, M., K. J. Van Zee, L. J. Solin, N. Houssami, M. Chavez-MacGregor, J. R. Harris, J. Horton, et al. 2016. “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.” Annals of Surgical Oncology 23 (12): 3801-3810. doi:10.1245/s10434-016-5449-z. http://dx.doi.org/10.1245/s10434-016-5449-z.1068-9265http://nrs.harvard.edu/urn-3:HUL.InstRepos:29408312Purpose Controversy exists regarding the optimal negative margin width for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery and whole-breast irradiation. Methods: A multidisciplinary consensus panel used a meta-analysis of margin width and ipsilateral breast tumor recurrence (IBTR) from a systematic review of 20 studies including 7,883 patients and other published literature as the evidence base for consensus. Results: Negative margins halve the risk of IBTR compared with positive margins defined as ink on DCIS. A 2-mm margin minimizes the risk of IBTR compared with smaller negative margins. More widely clear margins do not significantly decrease IBTR compared with 2-mm margins. Negative margins narrower than 2 mm alone are not an indication for mastectomy, and factors known to affect rates of IBTR should be considered in determining the need for re-excision. Conclusion: Use of a 2-mm margin as the standard for an adequate margin in DCIS treated with whole-breast irradiation is associated with lower rates of IBTR and has the potential to decrease re-excision rates, improve cosmetic outcomes, and decrease health care costs. Clinical judgment should be used in determining the need for further surgery in patients with negative margins narrower than 2 mm.en-USJournal Article2016-11-1810.1245/s10434-016-5449-z