New ASCO/ASTRO/SSO DCIS 2mm Margins Guideline is Not Really 2mm
(It’s actually “no ink on DCIS”)
The multidisciplinary margins panel guideline states, “Negative margins less than 2 mm alone are not an indication for mastectomy, and factors known to impact rates of ipsilateral breast tumor recurrence should be considered in determining the need for re-excision.” We agree with this statement from the panel. But the headlines universally associated with this guideline emphasize 2-mm margins, which compromises the panel’s stated goal of reducing unnecessary re-operations.
Read carefully, the guideline publication identifies positive “ink on tumor” margins as the actionable cutoff for re-operation for DCIS, the same as for invasive cancers. In fact, the panel emphasized that, although a negative margin of 2 mm may be associated with statistically lower local recurrence (LR) risk, this is not an indication for mastectomy or re-excision, unless other factors (e.g., “multiple close margins, and young patient age”) are judged to contribute an unacceptably high LR risk in an individual case.
The panel employed sound judgment when faced with balancing treatment morbidity, a statistical LR advantage for 2 mm, and the established “no ink on DCIS” guideline. So though a 2-mm margin may be ideal, their recommendation provided real-world advice: Negative margins less than 2 mm should trigger clinical review and judgment on an individual basis. As with invasive cancers, unless other factors indicate unusually high risk, a DCIS patient with negative margins, “no ink on DCIS,” needs no more surgery.
In the real world where we practice (in many places without a central lab), margin assessment is not only process dependent but observer dependent, and therefore may lack the uniformity to yield important differences between 2-mm margins and negative margins <2 mm. Moreover, the 2010 meta-analysis of randomized trials referenced by the panel proves that reducing local recurrence from 28% to 13% (with radiation) has literally no survival advantage (likely because only half of the 15% eliminated recurrences are invasive). In addition, newer molecular assays have been shown to refine individual recurrence risk assessment independent of traditional features like patient age, grade, and negative margin width. Assured that survival is excellent and not affected by additional treatments or surgery, a well-informed woman is afforded the chance to participate fully in decisions about her treatment after lumpectomy, now more than ever before.
Pat Whitworth, MD, FACS, director, Nashville Breast Center
Rakesh Patel, MD, Director, Radiation Oncology, Good Samaritan Hospital, Los Gatos, Calif.
Peter Beitsch, MD, FACS, Chairman, Targeted Medical Education