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

Monica Morrow,Kimberly J Van Zee,Lawrence J Solin,Nehmat Houssami,Mariana Chavez-Macgregor,Jay R Harris,Janet Horton,Shelley Hwang,Peggy L Johnson,M Luke Marinovich,Stuart J Schnitt,Irene Wapnir,Meena S Moran

doi:10.1016/j.prro.2016.06.011

Abstract

PurposeControversy exists regarding the optimal negative margin width for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery and whole-breast irradiation. Methods and materialsA multidisciplinary consensus panel used a meta-analysis of margin width and ipsilateral breast tumor recurrence (IBTR) from a systematic review of 20 studies including 7883 patients and other published literature as the evidence base for consensus. ResultsNegative 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. ConclusionUse 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.

Highlights

Breast-conserving therapy (BCT), defined as surgical excision of the primary tumor with a margin of surrounding normal tissue followed by whole-breast irradiation (WBRT), results in long-term cause-specific survival rates of greater than 95% for women with ductal carcinoma in situ (DCIS), as demonstrated in both randomized trials[1] and observational studies.[2,3]
Retrospective single-institution studies have suggested that a negative margin width of 1 cm or more may eliminate the reduction in ipsilateral breast tumor recurrence (IBTR) seen with WBRT,[9] leading some to conclude that larger margins are beneficial in patients undergoing WBRT
There are limitations to this guideline. It applies to patients with DCIS and DCIS with microinvasion (DCIS-M) treated with WBRT

Summary

Introduction

Breast-conserving therapy (BCT), defined as surgical excision of the primary tumor with a margin of surrounding normal tissue followed by whole-breast irradiation (WBRT), results in long-term cause-specific survival rates of greater than 95% for women with ductal carcinoma in situ (DCIS), as demonstrated in both randomized trials[1] and observational studies.[2,3] the addition of WBRT to surgical excision does not improve survival, it substantially reduces rates of ipsilateral breast tumor recurrence (IBTR), even among patients with smaller, non–high-grade DCISs.[1,4] Microscopically clear margins, defined as no ink on tumor, were required in 35‐7 of the 4 early randomized trials of WBRT for DCIS, but not in the fourth.[8]. Retrospective single-institution studies have suggested that a negative margin width of 1 cm or more may eliminate the reduction in IBTR seen with WBRT,[9] leading some to conclude that larger margins are beneficial in patients undergoing WBRT. Despite the widespread use of BCT for DCIS, there is still no consensus on what constitutes an optimal negative margin width.[10] As a consequence, approximately 1 in 3 women attempting BCT for DCIS undergo re-excision.[11] Re-excisions have the potential for added discomfort, surgical complications, compromise in cosmetic outcome, additional stress for patients and families, and increased health care costs and have been associated with conversion to bilateral mastectomy.[12]

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Results

Conclusion