- Guidelines regarding the minimal necessary margin width in the setting of breast-conserving surgery are an enormous contribution to improving the consistency and quality of breast cancer care.
- These guidelines do not eliminate the need for careful clinical judgment, individualized recommendations, and shared decisions in this context.
- Familiarizing ourselves with the evidence and rationale behind the guidelines and incorporating them into a true multidisciplinary approach while considering all relevant factors will maximize their potential and best serve our patients.
Debate has long surrounded the definition of an adequate microscopic margin around invasive and in situ breast cancer when performing breast-conserving surgery. Given the well-documented association between local recurrence and survival in breast cancer,1 many surgeons and radiation oncologists have previously been rigid in advocating for re-excision lumpectomies (and, when that cannot be accommodated, mastectomy). This choice is based on the perceived inadequacy of the measured width between the surgical margin and the cancer, but it is without a clear consensus as to what the actual margin width should be. This lack of consensus regarding the minimal margin width for breast conservation reflected limitations in data to help define when that margin was too close, along with the inherent imprecision of margin assessment, which is impacted by flattening of the specimen, tracking of surface ink, and variations in sampling, including the number of specimens sampled and the methods used. Thus, there was tremendous variation in when surgeons opted to return to the operating room for wider margins.2
To address this confusion, to target a potential driver of overuse of mastectomy, and to improve the consistent delivery of high-quality care to all patients with breast cancer, a multidisciplinary panel of experts from the Society of Surgical Oncology and the American Society for Radiation Oncology commissioned a systematic review and meta-analysis of the literature around which to base guidelines. In 2014, these groups published a consensus guideline for minimal margin width after excision of invasive breast cancer, advocating that “no tumor on ink” should be the standard in that context.3 This recommendation was not without controversy itself, as the meta-analysis that the guideline was based on demonstrated that close margins were associated with an increased risk of local recurrence compared with negative margins (odds ratio 1.74, 95% CI [1.42, 2.15]; p < 0.001).
Moreover, concerns were raised that this might be an underestimation, as the observational rather than randomized nature of the studies included in the meta-analysis made them vulnerable to selection bias. For example, patients who did not have re-excision for close margins might be more likely to include those with close deep margins where fascia was removed or those with favorable pathologic features, and patients with close margins may have been treated with higher doses of radiation therapy. Nevertheless, the guideline represented a transformative change toward harmonizing practice. With appropriate attention to these caveats, ASCO endorsed the guideline, which has led clinicians to abandon the routine re-excision of margins that are not frankly positive on ink.
More recently, a consensus panel from these organizations—together with ASCO—released a consensus guideline for the treatment of patients with ductal carcinoma in situ (DCIS), with the recommendation that 2-mm margins should be the standard for an adequate excision.4 This sparked some confusion, as following a lumpectomy for invasive breast cancer, the close margins are often not around the invasive cancer, but rather surrounding in situ disease. The panel argued that when invasive cancer is present, the vast majority of patients will receive systemic therapy, which further impacts local control rates. This highlights the importance of nuanced considerations of individual patient characteristics when applying such guidelines.
Improving Consistency of Care: Not One Size Fits All
Given the high rates of re-excision observed in patients with early-stage invasive cancer and those with DCIS, in the absence of clear benefit in reducing local recurrence and the wide variability in practice patterns, the development of consensus guidelines has been a tremendous step forward in quality improvement for breast surgery. This has the potential to reduce rates of re-excision and the costs of care.5 However, it is imperative that we not let the pendulum swing too far, with rigid adherence based on a cursory understanding of the data behind the guidelines. More than before, these guidelines highlight the importance of multidisciplinary management and individualization of care based on pertinent patient characteristics (both related to their clinical characteristics and their own preference or values). If the argument for not routinely obtaining margins greater than 2 mm for DCIS surrounding invasive cancer is the impact of systemic therapy, then it becomes even more important for the surgeon to communicate with the medical oncologist regarding the likelihood of that individual patient receiving systemic therapy.
Communication between the surgeon and the radiation oncologist is also critical. Similar to what we have seen with the management of a positive sentinel lymph node, a surgeon’s isolated decision not to re-operate leaves the radiation oncologist to decide whether to escalate radiation treatment—in this case, perhaps by performing a boost, or a higher-dose boost, than they might have administered otherwise. Before the guidelines, coordination between surgeons and radiation oncologists was an area of concern.6 The need for judicious interpretation of the guidelines emphasizes even more that multidisciplinary care coordination is a critical component of high-quality breast cancer care.
Understanding the meta-analysis, and the inherent limitations, makes it critically important to highlight that the interpretation should not be that “no tumor on ink” is an absolute standard for invasive cancer, but rather re-excision for “no tumor on ink” should no longer be routine. Many, if not most, patients with close margins can be spared re-excision, and early reports suggest that these rates are falling,7 but there will still be cases where re-excision should be considered. The guideline panels themselves have emphasized this in their own narratives, and it is critical that their efforts not be reduced to cursory skimming of recommendation tables alone.
Several factors, including multidisciplinary considerations, should be deliberated (Table). And although the irony is not lost in proposing that consensus guidelines should prompt more rather than less attention to individualized treatment, that is precisely the case. For example, a young woman with several close margins across a broad front should be strongly considered for re-excision, particularly if doing so would have a minimal impact on cosmesis. This is a two-way street, and thus the guidelines also should not be taken to mean that all cases of DCIS with margins less than 2 mm require a re-excision. Consideration of factors like the ones in the Table may support re-excision in one case but argue against re-excision in another. The panel emphasizes this important point in stating that clinical judgment should be used in determining the need for further surgery when DCIS margins are less than 2 mm.4
Guidelines regarding the minimal necessary margin width in the setting of breast-conserving surgery are an enormous contribution to improving the consistency and quality of breast cancer care. They help to simplify, although not eliminate, the difficulties surrounding decisions regarding re-excision. What must not be lost in these conversations is that such guidelines do not eliminate the need for careful clinical judgment, individualized recommendations, and shared decisions in this context.
No discussion of margins in breast cancer would be complete without consideration of the importance of minimizing the likelihood of close and positive margins to begin with. This is particularly true given the suggestion that local recurrence is higher in patients who undergo re-excision compared with patients who obtain negative margins in one operation.8 Several approaches can be used to help avoid both positive and close margins. The use of circumferential shave biopsies, encompassing the entire cavity, may serve to reduce the incidence of close or positive margins.9 Intraoperative margin analysis has the potential to greatly reduce re-excision rates without a dramatic increase in the volumes of excision.10 Novel technologies are presently being investigated that may further reduce the likelihood of needing to decide whether a re-excision is indicated.
In summary, the consensus guidelines on margins, like all guidelines in general, have great potential to increase standardization of practice and reduce the morbidity and cost associated with cancer care. Nonetheless, we must be careful not to fall into the trap of seeing guidelines as absolute and practicing “cookbook medicine.” Familiarizing ourselves with the evidence and rationale behind the guidelines and incorporating them into a true multidisciplinary approach while considering all relevant factors will maximize their potential and best serve our patients.
About the Authors: Dr. Sabel is the William W. Coon Collegiate Professor of Surgical Oncology in the Department of Surgery and the chief of the Division of Surgical Oncology with University of Michigan Health Systems. Dr. Jagsi is a professor and deputy chair in the Department of Radiation Oncology at the University of Michigan and a research investigator at the Center for Bioethics and Social Sciences in Medicine.