MIAMI – A wider margin width for women undergoing breast-conserving surgery without radiotherapy for ductal carcinoma in situ (DCIS) may be better for women than the 2-mm or greater margin width for women undergoing radiotherapy that was recently recommended in a draft consensus statement.
The draft consensus statement is currently under review by the Society of Surgical Oncology, the American Society for Radiation Oncology, the American Society of Clinical Oncology, and the American Society of Breast Surgeons, Dr. Kimberly Van Zee, who participated in the November consensus conference, reported at the annual Miami Breast Cancer Conference, held by the Physicians’ Education Resource.
The draft consensus statement does not address margin width in those who are not receiving radiotherapy because data are lacking in that population, but in her own retrospective review of nearly 3,000 cases, Dr. Van Zee found that “wider margin width is associated with a lower risk of recurrence among women not undergoing radiation.”
Her review, published in October (Ann Surg. 2015;262:623-31) and considered in the development of the draft consensus statement, included 2,996 consecutive women who underwent breast conserving surgery between 1978 and 2010. Of those, 363 experienced recurrence; 732 of the women were followed for at least 10 years, and the median follow-up period was 75 months, said Dr. Van Zee, a surgical oncologist at Memorial Sloan Kettering Cancer Center, New York.
After controlling for age, family history, clinical vs. radiologic presentation, nuclear grade, number of excisions, radiotherapy, endocrine therapy, and year of surgery, margin width was shown to be significantly associated with recurrence, she noted.
Women with larger negative margins had a significantly lower risk of recurrence vs. those with positive margins, she said.
An interaction between radiation therapy and margin width was significant, which indicates that the effect of margin width differs by use of radiation therapy, she noted.
Stratification by radiation therapy use demonstrated that the association of recurrence with margin width was significant in those not receiving radiation therapy, but not in those receiving radiation therapy.
Among those not receiving radiation therapy, a margin width of greater than 10 mm was associated with about a 60% reduction in recurrence, compared with those with negative margins of 2 mm or less.
The findings are important, because while DCIS has minimal mortality, recurrence rates after breast-conserving surgery are significant, and about half of recurrences are invasive, she explained.
“We know that negative margins are clearly a factor that’s associated with a lower risk of recurrence; the problem with all of our randomized trials and many retrospective studies is that margins have been categorized as positive or negative, so that doesn’t help us in determining what the optimal negative margin is,” she said.
Importantly, while radiation is known to reduce the rate of recurrence, that reduction is proportional.
“In every subset, radiation reduces risk by about half,” she said, noting that in patients with low risk, a 50% reduction may not be worth it.
Conference chair Dr. Patrick I. Borgen of Maimonides Medical Center in Brooklyn, N.Y., praised Dr. Van Zee’s work, saying that “without any question, that review will significantly impact the meta-analysis as we go forward and try to make some sense of what to do with our patients with DCIS.”
Dr. Van Zee reported having no disclosures. Dr. Borgen is on speakers bureaus for Genomic Health and NanoString Technologies.