The American Society of Clinical Oncology (ASCO), alongside the American Society for Radiation Oncology (ASTRO) and Society of Surgical Oncology (SSO), have released new guidelines clarifying the optimal negative margin width for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery and whole-breast irradiation (WBRT).
Numerous studies and clinical trials have demonstrated that breast-conserving therapy, defined as surgical excision of the primary tumor with a margin surrounding normal tissue followed by WBRT, can produce promising long-term survival for women with DCIS. However, while some 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), a consensus on what constitutes optimal negative margin width is lacking. This has led to many patients to receive toxic and costly procedures that may not provide any benefit.
Therefore, members of ASCO, ASTRO, and SSO convened a multidisciplinary panel (MP) to evaluate IBTR in relation to margin width and create a comprehensive guideline capable of assisting physicians and patients during the clinical decision-making process.
To form their recommendations, panel members followed 4 key steps of the guideline development process, including: (1) the development of a systematic review/study-level meta-analysis based on questions to be addressed by the MP to serve as the primary evidence base, with additional topic-specific literature reviews conducted by participants for questions not addressed in the meta-analysis; (2) the provision for each recommendation of a rating of the strength of the evidence and the strength of the recommendation; (3) the ascertainment of the level of agreement of panel members with each recommendation by vote, and the revision of recommendations to achieve greater than 90% consensus; and (4) the declaration by MP candidates of potential conflicts of interest before convening, and the obtaining of written disclosures at the consensus meeting (The co-chairs deemed no MP members had conflicts that could influence the process/development of specific recommendations).
Using these steps as a basis for the formulation of their review, the MP determined that negative margins may halve the risk of IBTR compared with positive margins defined as ink on DCIS. Additionally, tumors with a 2 mm margin may minimize the risk of IBTR compared with smaller negative margins while wider, clearer margins do not significantly decrease IBTR compared with the 2 mm margins. Further, margins less than 2 mm alone should not be considered an indication for mastectomy, and factors known to impact rates of IBRT should be considered in determining the need for re-excision.
Thus, panel members recommend 2 mm margins as the standard for DCIS treated with WBRT, which is associated with low rates of IBTR and has the potential to help patients avoid unnecessary and costly procedures.
However, members of the panel also noted that all of the studies included in the meta-analysis were retrospective, which may have limited their analysis. Still, despite the absence of any planned prospective randomized trials addressing the question of margin width and local recurrence, they still believe that their present recommendations provide the best, most evidence-based approach for clinical decision-making in patients with DCIS.
“With this guideline, it is our two-pronged goal to help physicians improve the quality of care they provide to women undergoing surgery for DCIS and ultimately improve outcomes for those patients. We hope the guideline also translates into peace of mind for women who will know that future surgeries may not be needed,” said Mariana Chavez-MacGregor, MD, University of Texas MD Anderson Cancer Center (Houston, TX), a panel member representing ASCO.
She added that women who are told they need a re-excision should ask what factors are prompting their doctor to recommend that decision.
“This guideline is another important step in our collective work to ensure that women are receiving the best and most appropriate breast cancer care,” said Judy Salerno, MD, MS, president and chief-executive officer of Susan G Komen, the organization that also provided funding for the development of the guidelines.