Study Challenges Need for Preventive Bilateral Mastectomy in Women with DCIS

The use of bilateral mastectomy — surgical removal of both breasts — has more than doubled in the past 10 years in women with ductal carcinoma in situ (DCIS), according to data from the National Cancer Database.

Many of the women are choosing to undergo the radical surgery in order to reduce their risk of developing contralateral breast cancer (CBC), a second cancer in the opposite breast. Per the American Cancer Society, removing both breasts before cancer is diagnosed can reduce the risk of breast cancer by up to 97 percent. However, a new study finds that this may be an unnecessary surgery in patients with DCIS.

DCIS, stage 0 cancer, is highly curable. It is non-invasive, which means the cells that line the ducts have changed to look like cancer cells, but they have not spread through the walls of the ducts into the nearby breast tissue.

In the study, a team of researchers from Memorial Sloan Kettering Cancer Center (MSK) in New York City examined the risk of CBC after DCIS in more than 2,750 patients, particularly in women treated with breast-conserving surgery between the years of 1978 to 2011.

They evaluated outcomes in terms of CBC, defined as either DCIS or invasive cancer, as well as the rates of CBC compared with the rates of ipsilateral recurrence — cancer in the same breast.

Researchers determined that, for women who underwent breast conservation for DCIS, 3.2 percent developed a contralateral cancer after five years. After 10 years, 6.4 percent had developed CBC.

Investigators evaluated factors potentially associated with the development of CBC or ipsilateral recurrence: age over or under 50 years, presentation of the cancer via imaging versus clinical examination, family history, the nuclear grade of the DCIS, surgery before or after 1999, and the use of radiation and/or endocrine therapy. Of those, age, family history, presentation and initial DCIS characteristics did not correlate with new tumors in the second breast. But, the study concluded that some of these factors were associated with cancer returning in the original breast.

A multivariable analysis confirmed that the only factor associated with the risk of CBC was endocrine therapy. Its use nearly halved the contralateral risk, noted lead author Megan Miller, M.D., of MSK.

The researchers then looked at the risk of CBC in women who had ipsilateral recurrence, a total of 331 women in this study. Measuring from the time of recurrence, 3.7 percent experienced contralateral recurrence after five years and 8.1 percent had developed contralateral recurrence after 10 years — similar to the rates for study participants overall.

Analyzing the time period from diagnosis with DCIS to any next breast cancer event in each patient, investigators found that the risk of ipsilateral recurrence was two-and-a-half times greater than that of contralateral cancer. Among women that did not receive radiotherapy, the risk of ipsilateral recurrence was four times greater.

The authors concluded that there is low risk of CBC after DCIS for women treated with breast-conserving surgery. In addition, the rate of CBC is not higher after ipsilateral recurrence.

“Factors associated with ipsilateral recurrence are not associated with any contralateral cancer, including invasive disease,” Miller said. “While factors associated with ipsilateral risk are important in decision-making regarding management of initial DCIS, they are not an indication for prophylactic bilateral mastectomy.”