New SSO-ASTRO-ASCO Clinical Practice Guideline Clarifies the Question of Margins for Breast-Conserving Surgery in Ductal Carcinoma in Situ



In 2014, the Society of Surgical Oncology (SSO) and the American Society for Radiation Oncology (ASTRO) published a “Consensus Guideline on Margins for Breast-Conserving Surgery With Whole-Breast Irradiation in Stages I and II Invasive Breast Cancer.”1 A multidisciplinary expert guideline used a meta-analysis of margin width and ipsilateral breast tumor recurrence from a systematic review of 33 studies including 28,162 patients as the primary evidence base for the consensus. This meta-analysis found that positive margins (ink on invasive carcinoma or ductal carcinoma in situ) were associated with a twofold increase in the risk of ipsilateral breast tumor recurrence compared with negative margins.

 

Clinical judgment should be used in determining the need for further surgery in patients with negative margins < 2 mm.
— Jay R. Harris, MD

Practice-Changing Guideline

This increased risk was not mitigated by favorable biology, endocrine therapy, or a radiation boost. More widely clear margins did not significantly decrease the rate of ipsilateral breast tumor recurrence compared with no ink on tumor. The expert panel concluded that the use of no ink on tumor as the standard for an adequate margin in invasive cancer in the era of multidisciplinary therapy is associated with low rates of ipsilateral breast tumor recurrence and has the potential to decrease reexcision rates, improve cosmetic outcomes, and decrease health-care costs. 

This consensus guideline was practice-changing and decreased the use of reexcision across the country. The American Society of Clinical Oncology (ASCO) endorsed this guideline but recommended greater emphasis on the importance of postlumpectomy mammography for cases involving microcalcifications and called for flexibility in the application of the guideline.2 In particular, they cited the example of a young woman with multiple very close margins of less than 1 mm across a broad front, an extensive intraductal component, and large breasts that would easily accommodate a reexcision. 

Of note, this guideline specifically did not refer to patients with ductal carcinoma in situ or patients with invasive breast cancer treated with preoperative systemic therapy.

Second Panel

To address the question of margins in patients with ductal carcinoma in situ, a second expert guideline panel was convened and similarly used a meta-analysis of margin width and ipsilateral breast tumor recurrence from a systematic review of 20 studies including 7,883 patients with ductal carcinoma in situ and other published literature as the evidence base for consensus.3-5 This SSO-­ASTRO-ASCO Consensus Guideline was recently reported by Morrow and colleagues and is summarized in this issue of The ASCO Post. 

The new expert guideline panel found that negative margins halved the risk of ipsilateral breast tumor recurrence compared with positive margins defined as ink on ductal carcinoma in situ. A 2-mm margin minimized the risk of ipsilateral breast tumor recurrence compared with smaller negative margins. More widely clear margins did not significantly decrease ipsilateral breast tumor recurrence compared with 2-mm margins. Negative margins less than 2 mm alone are not an indication for mastectomy, and factors known to impact the rates of ipsilateral breast tumor recurrence should be considered in determining the need for reexcision. 

The panel concluded that the use of a 2-mm margin as the standard for an adequate margin in ductal carcinoma in situ treated with whole-breast radiation therapy is associated with low rates of ipsilateral breast tumor recurrence and has the potential to decrease reexcision rates, improve cosmetic outcome, and decrease health-care costs. Clinical judgment should be used in determining the need for further surgery in patients with negative margins < 2 mm. 

The specific recommendations as well as the strength of recommendations and associated evidence are summarized in the accompanying article in this issue of The ASCO Post. ■

Disclosure: Dr. Harris reported no potential conflicts of interest.

Dr. Harris is Professor of Radiation Oncology at Dana-Farber Cancer Institute and at Brigham and Women’s Hospital, and Distinguished Professor at Harvard Medical School.

References

1. Moran MS, Schnitt SJ, Giuliano AE, et al: Society of Surgical Oncology-American Society for Radiation Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in stages I and II invasive breast cancer. J Clin Oncol 32:1507-1515, 2014.

2. Buchholz TA, Somerfield MR, Griggs JJ, et al: Margins for breast-conserving surgery with whole-breast irradiation in stage I and II invasive breast cancer: American Society of Clinical Oncology endorsement of the Society of Surgical Oncology/American Society for Radiation Oncology consensus guideline. J Clin Oncol 32:1502-1506, 2014.

3. 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. August 15, 2016 (early release online).

4. 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. Ann Surg Oncol 23:3801-3810, 2016.

5. 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. Pract Radiat Oncol 6:287-295, 2016.


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A positive margin, defined as ink on ductal carcinoma in situ, is associated with a significant increase in ipsilateral breast tumor recurrence; this increased risk is not nullified by the use of whole-breast irradiation.
— Monica...


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