We are trying to provide data to help women with [ductal carcinoma in situ] understand their risk and not be driven by anxiety or fear.— Megan Miller, MD
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An increasing number of women with ductal carcinoma in situ are undergoing contralateral mastectomy, but the 5-year risk of cancer in the opposite breast is only about 3%, a study from Memorial Sloan Kettering Cancer Center recently found.1 Investigators hope these numbers will dissuade women from opting for this presumably unnecessary surgery.
“We found a very low risk of contralateral breast cancer after [ductal carcinoma in situ] for women treated with breast-conserving surgery—3.2% at 5 years and 6.4% at 10 years—irrespective of age, family history, and characteristics of the initial [ductal carcinoma in situ],” said Megan Miller, MD, a breast surgical oncology fellow at Memorial.
At the 2017 American Society of Breast Surgeons (ASBrS) Annual Meeting, Dr. Miller presented a study that aimed to calculate the risk of contralateral cancer specifically in women with ductal carcinoma in situ who were candidates for breast-conserving surgery. Most previous studies have evaluated the risk in women with invasive breast cancer. “We have not had this information before,” she said. “We are trying to provide data to help women with [ductal carcinoma in situ] understand their risk and not be driven by -anxiety or fear. Our research provides important data for treatment decision-making,” Dr. Miller told The ASCO Post.
The analysis was based on 2,759 patients with ductal carcinoma in situ undergoing breast-conserving surgery at Memorial Sloan Kettering from 1978 to 2011. At a median follow-up of 6.8 years, 127 developed contralateral breast cancer and 331 had an ipsilateral recurrence. This translated into a 2.5 times higher risk for ipsilateral recurrence over contralateral cancer, she noted.
The investigators also used a “competing risk model” to calculate the risk of contralateral disease. This showed the 5-year risks to be 7.8% for ipsilateral recurrence and 2.9% for contralateral cancer and the 10-year risks to be 14.5% and 5.8%, respectively. Risk of invasive disease was 2.8% for ipsilateral recurrence and 2.0% for contralateral cancer at 5 years, and 6.1% and 4.1%, respectively, at 10 years.
This model also highlighted the benefit of radiation therapy after lumpectomy. In patients forgoing radiotherapy, ipsilateral recurrences were observed in 19.5% and contralateral cancers, in 5.2%.
The study found that even for the 331 women who developed an ipsilateral recurrence after treatment for ductal carcinoma in situ, the risk of subsequent contralateral breast cancer was low. The 5-year and 10-year rates of subsequent contralateral breast cancer were 3.7% and 8.1%, respectively, which were not significantly different from the risk in the entire cohort of 2,759 patients.
Endocrine Therapy Impacts Outcome
For ipsilateral recurrence, several risk factors were identified, including younger age, clinical (vs radiologic) presentation, intermediate/high (vs low) nuclear grade, surgery performed before 1998, absence of radiotherapy, and absence of endocrine therapy. For contralateral risk, however, endocrine therapy was the only influential factor. Patients with ductal carcinoma in situ receiving endocrine therapy had a 39% reduced risk of contralateral cancer (P = .07) and a 41% reduced risk of ipsilateral recurrence (P = .004), she reported.
The study concluded that while factors associated with ipsilateral breast cancer recurrence are important in designing treatment for the initial ductal carcinoma in situ, they are not an indication for contralateral prophylactic mastectomy. ■
Disclosure: Dr. Miller reported no conflicts of interest.
Julie Margenthaler, MD
“This study of 2,759 patients with ductal carcinoma in situ provides data for women who are considering their surgical options,” said Julie Margenthaler, MD, a breast surgeon at Washington University of Medicine, St. Louis, and Communications Chair of the American...