New Consensus Guidelines on DCIS Establish Ideal Surgical Margins

Mary L. Gemignani, MD

Barbara L. Smith, MD, PhD

The American Society of Clinical Oncology (ASCO), the Society of Surgical Oncology (SSO), and the American Society for Radiation Oncology (ASTRO) together released a new surgical guideline for women diagnosed with ductal carcinoma in situ (DCIS). After reviewing published data, the authors of the consensus statement now recommend a 2 mm negative surgical margin for patients with DCIS who receive breast-conserving surgery and whole-breast radiotherapy, which protects patients from tumor recurrence.

We are joined today by Mary L. Gemignani, MD, a surgical oncologist who specializes in breast cancer at the Memorial Sloan Kettering Cancer Center in New York, and Barbara L. Smith, MD, PhD, surgical oncologist and director of the women’s breast program at the Massachusetts General Hospital in Boston, to discuss the new guideline. Neither Dr. Gemignani nor Dr. Smith were involved in helping to pen the consensus statement.

- Interviewed by Anna Azvolinsky

Cancer Network: Dr. Gemignani, let’s start with you. Can you talk about the issue of surgical margins in surgery for women with DCIS. Do breast surgeons generally agree on the margins to use?

Dr. Gemignani: When we talk about margins we are usually just referring to breast-conserving surgery, commonly termed a lumpectomy. It is a surgical excision of the area, in this case that has a DCIS, with a margin of normal surrounding breast tissue, and this is usually followed with whole-breast radiation therapy. It is known that negative margins are associated with a twofold decrease in recurrence in the treated breast. However, there is a lot of controversy among breast surgeons as well as other treating physicians like radiation oncologists in the medical community regarding what really constitutes a negative margin width. Consequently, there is a significant variability in the United States among surgeons and really, about one in three women who chose breast-conserving surgery for DCIS undergo additional surgery to clear margins, which is called a re-excision. So the problem is that these additional surgeries have the potential for surgical complications, stress for the patient and their family, as well as compromising cosmetic results. And I think that is what drove the decision to come up with a more uniform consensus.

Dr. Smith: I think the other piece to this is that we are beginning to learn that we might need to apply different margin standards to women with DCIS than to women with pure invasive cancer, and that is a result of the geometry of the tumor. As Dr. Gemignani said, it is really important to get microscopically free margins to reduce recurrence, and it is challenging to do that with DCIS because it grows not as a little ball that gradually gets bigger and that is easier to remove completely, but it grows as little strands of tissue inside the milk ducts where you can’t see them, and they may not be visible or apparent on imaging study. So the challenge is that you are looking for something microscopic, and you really want to get it all out and that is difficult. Coming up with a consensus for the best way to do that has been challenging.

Cancer Network: Dr. Smith, could you take us through the key points of this new guideline?

Dr. Smith: So the guideline is now reinforcing old standards that you need at least a 2 mm clear margin, microscopically, all the way around the edges of the lumpectomy. So there is no spot where you want tumor cells closer than 2 mm to the margin of the lumpectomy specimen. This was an old standard that was applied, and for invasive cancers we’ve actually discovered that we can allow a narrower margin, and these guidelines are really reaffirming that DCIS is different because of its growth patterns and requires this wider margin. It also, I think, helps standardize previous concerns that Dr. Gemignani mentioned, that there were some people that thought you had to have much wider margins, perhaps 5 or even 10 mm, which starts to be deforming of the breast.

Cancer Network: For which patients are the recommendations maybe not so clear cut?

Dr. Gemignani: I think that the guidelines are aimed really at patients who are going to get radiation therapy and so, when we look at other factors that fall outside of that, then you don’t really apply these guidelines. But I also think that there is a lot of room for clinical judgment, which is a good thing about these guidelines. So, in cases where margins are negative but not really 2 mm, it allows the breast surgeon to use additional clinical information such as post-excision mammography in cases where calcifications were associated with DCIS, which margin it is, the anatomical location of it. Sometimes if the surgeon goes down to the chest wall, to the muscle, that posterior margin may be narrower or close but that doesn’t necessarily have to be re-excised, because the surgeon would know that they went deeply into the area of the breast tissue. And so other things like cosmetic impact as well as patients’ overall life expectancy factor in. I think the guidelines’ allowing of clinical judgment for negative margins that are not 2 mm is a good thing.

Dr. Smith: I would add that there is an opportunity for the radiation oncologist to compensate for a narrower margin in some cases by adding a larger boost of radiation as a part of the standard radiation treatment. So there are some ways that judgment can be adjusted with this. I’d say the one other group where this might raise some discussion are the patients that have an invasive cancer, but then have a lot of DCIS around the lump itself. The original guidelines for invasive cancer patients said that you’d need only no tumor on ink for those patients that are invasive with or without DCIS associated with it, that no tumor on ink is an acceptable margin. This may get us back to discussing a little bit more patients that have a lot of DCIS, or what used to be called an extensive intra-ductal component, because those are another group of patients where you might have a harder time getting clean margins and this very narrow margin might not be sufficient in all cases.

Cancer Network: Are there still other questions on surgery and margins in DCIS that remain for these women?

Dr. Gemignani: Yes, I think one of the things that the guideline also points out is that there is not a lot known about association between women who take tamoxifen, and drugs like those that are known to reduce cancer risk and recurrence, and what is the width of the margin or the type of radiation and the delivery techniques that are used, or even age and histologic factors. So I think there are some questions remaining about those kind of scenarios, and as I mentioned and as was brought up, these guidelines don't really address any issues related to patients who forego radiation.

Dr. Smith: I would add that one of our own research projects being published just this month looked at lumpectomy specimens in our practice where the doctor took shaved margins all the way around that main lumpectomy specimen so that we could say, “What did the margin look like on the main specimen, and then what did you find when you took another slice beyond that?” And we found that if you had a 2 mm margin for DCIS, about 14% of cases still showed some additional DCIS cells outside of the original lumpectomy margin, whereas if the margin was less than 2 mm, but no tumor on ink, it was 50% that had residual disease, and if there was tumor on ink, it was 77%.

So we don’t know how much these little spots of DCIS-that we’ve always known we’ve left some of behind-we don’t know how the number of these or the amount of material left behind actually affects outcomes when women are having radiation. So we are still learning how radiation can compensate in terms of margins and what is a safe amount to leave. This is all colored by the fact that DCIS is a curable disease, so we don’t want to let it turn into anything else, or progress, but at the same time we don’t want to overtreat it, which is also has been a concern among some circles, that perhaps DCIS doesn't need as much treatment as we are already giving.

Cancer Network: Thank you both so much for joining us today to discuss this important topic.

Dr. Smith: Thank you.

Dr. Gemignani: Thank you.