Findings from a controversial study suggest that women who have lumpectomy to remove ductal carcinoma in situ (DCIS) are less likely to have cancer come back in the same breast when at least 10 mm (about a half inch) of cancer-free tissue around the DCIS is removed during surgery. The results were published March 22, 2012 in the online edition of the Journal of the National Cancer Institute.
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."
Women diagnosed with DCIS have very good prognoses. Ten years after DCIS diagnosis, 98% to 99% of women will be alive.
This study was a meta-analysis -- a study that combines and analyzes the results of many earlier studies. In this case, results of more than 7,500 women in 21 research studies published between 1970 and 2010 were analyzed. All the women had been diagnosed with DCIS and had lumpectomy to remove the cancer.
The meta-analysis found that women with clean margins of 10 mm or larger at lumpectomy were 54% less likely to be diagnosed in the future with breast cancer in the same breast (called ipsilateral recurrence) compared to women who had clean margins smaller than 10 mm.
While these results seem to suggest that larger clean margins are better when DCIS is removed, the results are controversial for several reasons.
Many of the women participating in the studies were diagnosed decades ago when breast cancer screening and treatments weren't as effective as they are now. For women diagnosed decades ago, larger margins may have affected prognosis more because the DCIS was larger at the time of diagnosis and other treatments -- such as radiation therapy and hormonal therapy -- weren't used as optimally as they are now.
Also, more of the women in the meta-analysis who had surgical margins larger than 10 mm came from more recent studies. Their prognosis may have been better not because of the larger margins but because of better, earlier diagnosis and treatment.
Given the overall excellent prognosis of women diagnosed with DCIS, doctors will likely view the study's results with some caution. Trying to remove clean margins 10 mm or larger during DCIS surgery could result in more women having repeat surgery, more unhappiness with cosmetic results after DCIS lumpectomy, and more women unnecessarily having mastectomy instead of lumpectomy to remove DCIS.
If you've been diagnosed with DCIS, your doctor will recommend both the type of surgery and the treatments after surgery that make the most sense for you, based on your specific recurrence risk and overall prognosis. If the DCIS will be removed by lumpectomy, you may want to ask your surgeon about the plan for the margins and how your individual situation influences that plan. Your DCIS treatment plan after surgery may include radiation therapy, hormonal therapy, both, or neither.
If you're deciding on treatments after DCIS surgery, you might want to ask your doctor if the Oncotype DX test might help figure out if you would benefit from radiation therapy. Research has shown that the Oncotype DX test, a genomic test done on DCIS tissue, does a good job of predicting the risk of cancer recurrence and helping doctors judge who is most likely to benefit from radiation therapy after lumpectomy to remove DCIS.
Armed with the best information possible, you and your doctor can decide on a treatment plan that makes the most sense for your unique situation.
The Breastcancer.org DCIS pages contain more information on DCIS symptoms, diagnosis, and treatment.
Editor's Note: To help standardize the definition of negative margins, the American Society for Radiation Oncology and the Society of Surgical Oncology issued new guidelines in February 2014 saying that clear margins, no matter how small as long as there was no ink on the cancer tumor, should be the standard for lumpectomy surgery.