Two controversial areas in the management of ductal carcinoma in situ (DCIS) involve appropriate negative margin width for conservative surgery and whether surgery is indicated in all cases with this diagnosis. Pure DCIS is a high-risk breast lesion as it can sometimes be associated with later development of invasive breast cancer in the absence of treatment. Recent national practice guidelines suggest that adequate margins for DCIS should be ≥2 mm after breast-conserving surgery followed by radiotherapy (RT). This guideline is being utilized by many groups as an absolute indication for additional surgery, although clinical judgment was recommended. We evaluated contemporary patient local recurrence outcomes at The University of Texas MD Anderson Cancer Center. The cases had been handled using multidisciplinary DCIS practices, including extensive preoperative, intraoperative pathologic image-guided assessment of margins; offering some patients with small low- or intermediate-grade DCIS the option of no RT; the use/magnitude of radiation boost tailored to margin width; and offering endocrine therapy for estrogen receptor–positive DCIS. Use of these MD Anderson practices has resulted in 10-year local recurrence rates below 5% for patients with margins <2 mm who received RT. Patients with margins <2 mm who do not receive RT experience significantly higher local failure rates, in the 30% range, and are recommended to repeat surgery. Individualized patient care is determined by a multidisciplinary team and there is not an absolute requirement to achieve wider negative surgical margins when margins are found to be <2 mm if the patient will be treated with RT. Globally, there are at least 3 clinical trials ongoing that are testing the hypothesis that biopsy alone with active surveillance is not inferior to immediate breast-conserving surgery with or without radiotherapy for DCIS. In the United States, one study is the COMET trial, run by the Alliance Foundation Trials group. COMET is a randomized trial in which 1200 patients over age 40 years with hormone-positive DCIS, without a mass lesion, will have stereotactic core biopsy; they will then receive guideline-concordant care versus no surgery, with choice of endocrine therapy and close follow-up. The primary endpoints for these trials are invasive breast cancer recurrence.
The management of ductal carcinoma in situ (DCIS) is one of the most controversial areas in breast cancer management. It is curious that on the one hand we continue to debate whether 1 or 2 mm margins are clinically relevant compared with no tumor on ink for breast conservation, and at the same time, we have begun randomized trials of biopsy alone for DCIS without surgery—just active surveillance. Taken together, this suggests that many therapeutic questions and potential areas for clinical care improvements remain in this field.
Margins for DCIS
For invasive breast cancer, national consensus guidelines state that negative margin width is considered adequate when the tumor is not present on ink when patients are receiving breast-conserving surgery followed by whole breast radiotherapy (RT).1
These guidelines have definitely resulted in fewer repeat surgeries and mastectomies in the United States.2
However, there is concern regarding the new margin guideline recently endorsed—an optimal margin width of DCIS of 2 mm—by the Society of Surgical Oncology, the American Society of Radiation Oncology, and the American Society of Clinical Oncology.3
The guideline clearly stated that individualized patient decisions based on clinical judgment should be utilized. The main issue that has been raised is that it is a paradox to have 2 different margin guidelines—one for invasive cancer with DCIS, and another for pure DCIS—when receiving postoperative RT. These guidelines were based on a meta-analysis of retrospective studies beginning in the 1960s. Theoretically, differences in margin guidelines for negative margin width for pure DCIS have to do with early pathologic studies related to multifocality seen in pure DCIS, but this pathologic finding also applies when DCIS accompanies invasive breast cancer.