15 August 2016
A consensus statement was released today by the Society of Surgical Oncology, the American Society for Radiation Oncology, and the American Society of Clinical Oncology. It addresses the issue of surgical margins for patients undergoing breast conserving surgery (lumpectomy) for ductal carcinoma in-situ (DCIS). The summary notes “Use 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 [in-breast tumor recurrence, also known as local recurrence] 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.”
We know from many years of research that women who undergo lumpectomy have the same survival rates as those who undergo complete breast removal. When a lumpectomy is performed, the goal is to remove the tumor with a rim of normal breast tissue (margin). It has long been debated how much margin is needed. If clear margins are not obtained, repeat surgery is usually recommended, and due to lack of standardized guidelines, re-excision has been recommended for many patients with close margins. Nationally re-excision rates have been reported as high as 50%. Additional surgery increases the likelihood of complications, increases overall breast cancer treatment time, and may have a negative impact on cosmetic results.
In 2014, margin guidelines were published for invasive breast cancer, and they noted that for patients with early stage breast cancer undergoing lumpectomy and radiation therapy, “no ink on tumor” is an acceptable margin. Today’s DCIS statement notes that a 2mm margin is acceptable in most cases of non-invasive cancer. Why the discrepancy? Shouldn’t invasive cancer be treated with a wider margin than DCIS? An important distinction between invasive cancer and DCIS is that DCIS lesions are more likely to have “skip areas”, so a clear margin may not be as predictive of a low likelihood of residual disease. However, just as with the invasive cancer guidelines, the current consensus guideline notes that wider margins do not improve outcomes.
Both the invasive and DCIS statements apply to patients with stage I and II breast cancer, undergoing lumpectomy with postoperative radiation therapy. Without radiation therapy, the risk of local recurrence (the same cancer returning in the breast) can be as high as 30-40%. However, there are certain situations when radiation therapy may not be recommended, depending on tumor type, patient age, and other factors.
As with other clinical practice guidelines, the current statement is not a substitute for good clinical judgement and multidisciplinary case discussion. There are situations when a smaller margin may be acceptable, and settings where a larger margin may be desired for various reasons. However, patients and physicians need to be aware that more surgery is not better when it comes to breast cancer treatment. Dr. Monica Morrow, lead author on the statement, advised that “if a woman with a negative margin is told to have a re-excision, she needs to ask what factors are prompting the surgeon to recommend that re-excision.”