A new guideline put out by three national cancer organizations says that 2-millimeter (about one-eighth of an inch) clean margins should be the standard for women diagnosed with ductal carcinoma in situ (DCIS) treated with lumpectomy and whole-breast radiation.
The guideline was published online on Aug. 15, 2016 by the Journal of Clinical Oncology. Read “Society of Surgical Oncology–American Society for Radiation Oncology–American Society of Clinical Oncology Consensus Guideline on Margins for Breast-Conserving Surgery With Whole-Breast Irradiation in Ductal Carcinoma In Situ.”
DCIS isn’t invasive cancer. DCIS can be large or small, but stays inside the breast milk duct. It doesn’t spread into surrounding normal breast tissue or into the lymph nodes or other organs. Still, anyone diagnosed with DCIS is at higher risk of developing invasive breast cancer in the same breast compared to someone who hasn’t had DCIS. DCIS also is called stage 0 breast cancer.
DCIS usually is treated by lumpectomy, often followed by radiation therapy. If the DCIS is large, a mastectomy may be recommended. Chemotherapy usually isn't recommended after surgery for DCIS. Hormonal therapy may be recommended if the DCIS is hormone-receptor-positive. During lumpectomy, the surgeon removes the cancer tumor and some of the normal tissue that surrounds it (called the margins). After lumpectomy, a pathologist carefully examines the tissue that was removed to see if cancer cells are present in the margins. Margins that are free of cancer are called "negative" or "clean." Margins that have cancer cells in them are called "positive." If the margins are positive, more surgery may be recommended to get clean margins.
Women diagnosed with DCIS have very good prognoses. Ten years after DCIS diagnosis, 98% to 99% of women will be alive.
The new guideline was put out by the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Surgical Oncology (SSO). All three groups are national organizations of oncologists, radiologists, surgeons, and other cancer care providers. Guidelines from these groups give doctors recommendations for treatments and testing that are supported by much credible research and experience.
To create the guideline, experts from the three groups reviewed available research, including 20 studies involving 7,883 women.
The guideline says that a 2-millimeter clean margin offers enough protection against the DCIS coming back (recurrence) for women treated with lumpectomy and whole-breast radiation. Clean margins that are wider than 2 millimeters don’t further reduce the risk of recurrence according to the guideline.
The experts put out the guideline because there has been disagreement on how big clean margins should be for DCIS. About one in three women treated for DCIS have more surgery because their doctors feel that the clean margins should be wider.
"An important finding from the review of the published literature performed to provide evidence for this guideline is that margin widths greater than 2 millimeters do not reduce the risk of cancer recurring in the breast in women with DCIS who are treated with lumpectomy and whole breast radiation therapy," said Monica Morrow, M.D., of the Memorial Sloan Kettering Cancer Center and one of the authors of the guideline.
"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," said Mariana Chavez-MacGregor, M.D., of the University of Texas MD Anderson Cancer Center who also helped write the guideline. "We hope the guideline also translates into peace of mind for women who will know that future surgeries may not be needed."
Besides recommending that standard for clean margins be 2 millimeters, the guideline also says:
- A positive margin is associated with a much higher risk of DCIS recurrence.
- Treatment with surgery alone, no matter how wide the clean margins, is linked to a higher risk of recurrence compared to treatment with surgery and whole-breast radiation.
- Treatment with hormonal therapy can reduce the risk of recurrence, but no data show a link between hormonal therapy and the width of clean margins.
- The width of the clean margins shouldn’t affect the type of whole-breast radiation a woman receives.
- DCIS with microinvasion (DCIS-M) should be considered DCIS when deciding on optimal margin width. DCIS with microinvasion means that a few of the cancer cells have started to break through the wall of the duct. This is considered to be a slightly more serious form of DCIS.
The experts also were careful to explain exactly for whom the guideline applied: "It applies to patients with DCIS and DCIS-M treated with whole-breast radiation therapy," they wrote. "The findings should not be extrapolated to patients with DCIS treated with accelerated partial breast irradiation or those with invasive carcinoma for whom a separate guideline has been developed."
If you’ve been diagnosed with DCIS, this guideline is reassuring. You and your doctor will consider which type of surgery makes sense for you based on your unique situation. For many women, lumpectomy followed by whole-breast radiation is a good option. This guideline offers peace of mind that you likely won’t need more surgery after lumpectomy if you have clear margins of at least 2 millimeters.
For more information on DCIS and how it’s treated, visit the Breastcancer.org DCIS pages.