The rate of contralateral prophylactic mastectomies (CPMs) in women with unilateral breast cancer in the U.S. increased by a whopping 150% between 1998 and 2003.¹ This suggests the widespread adoption of aggressive surgical intervention in an attempt to reduce risk or prevent cancer in the noncancerous breast.

This trend isn’t endorsed by the National Comprehensive Cancer Network’s breast cancer guidelines, however, which discourage prophylactic mastectomy in most women. The removal of a noncancerous breast is recommended only in women who are considered at high risk for contralateral breast cancer.²

CPM is no longer being exclusively performed on high-risk patients, however. More low-risk women are opting for this aggressive approach.³This trend is occurring even in light of a low likelihood of a second primary breast cancer. Data suggest that the 10-year cumulative risk of contralateral breast cancer is approximately 4% to 5%, and possibly lower for women diagnosed in 2014.⁴

In light of the increasing use of CPM, the obvious question is: Does a double mastectomy improve survival? According to a recent assessment of data obtained for nearly 190,000 women with early-stage, unilateral breast cancer from the California Cancer Registry, the answer is no. Kurian and colleagues found no survival benefit with bilateral mastectomy compared with breast-conserving surgery plus radiation. And consistent with other data showing increasing trends, the authors reported that the rate of bilateral mastectomy increased from 2% in 1998 to 12.3% in 2011, reflecting an annual increase of 14.3%. The rate increase was highest among women younger than 40 years, jumping from 3.6% in 1998 to 33% in 2011, for an annual increase of 17.6%. By comparison, unilateral mastectomy was found to be the least popular option, decreasing in all age groups and yielding a lower survival rate.⁵ With regard to this last finding, the authors said they agreed with other researchers that patients whose tumors exhibit signs consistent with a poorer prognosis are more likely to have unilateral mastectomy than breast conservation—and are also more likely to have a poorer survival.

In contrast, Kruper and colleagues reported improved disease-specific and overall survival (OS) in women who underwent CPM. In this study, the Surveillance, Epidemiology, and End Results database was used. The researchers identified approximately 27,000 patients with unilateral breast cancer who underwent a mastectomy with or without CPM between 1998 and 2010. Notably, group differences in OS were greater than the group differences for disease-specific survival, a finding reported to be consistent with selection bias. The authors noted that the observed survival benefit may be attributed to healthier women being chosen or recommended for CPM.⁶

In a small, single-center study, 237 women younger than 40 years who were diagnosed with breast cancer at Mount Sinai Medical Center in Miami Beach, Fla., between 1980 and 2010 were identified. Zeichner and colleagues found that CPM provided an OS advantage after 10 years of follow-up but not after 5 years, regardless of genetics, tumor, and patient characteristics.⁷

Not surprisingly, women seem to be choosing CPM in hopes of extending survival. According to a survey conducted by Rosenberg and colleagues of women aged 40 or younger, 94% reported that improving survival was an extremely or very important factor in their decision to undergo CPM. Only 18% of respondents, however, believed that women who undergo CPM would live longer than those who do not. So while there’s a clear motivation to undergo CPM to improve survival, the majority of women seem to believe that CPM may not extend their lives. Additionally, women without BRCA mutations tended to overestimate their risk of contralateral breast cancer, while women with a known BRCA mutation more accurately perceived their risk.⁸

The survey also found that the desire to decrease the risk of contralateral breast cancer and get peace of mind both ranked high in the respondent’s decision to undergo CPM (in 98% and 95% of women, respectively). Overall, the women surveyed were satisfied with their decision, with 80% indicating extreme confidence.⁸

“There are several potential reasons for this trend,” said Todd M. Tuttle, MD, of the Division of Surgical Oncology, Department of Surgery, at the University of Minnesota in Minneapolis. Among those he cited were:

• improvement in mastectomy and reconstruction techniques
• increased awareness of hereditary breast cancer
• increased use of magnetic resonance imaging, which has raised doubts about the contralateral breast
• overestimation of the risk of contralateral breast cancer
• overestimation of the survival outcomes of bilateral mastectomy.

The debate over whether CPM improves survival will likely continue. Despite mixed survival-advantage data, there’s a clear, increasing trend in women diagnosed with unilateral breast cancer to choose this more aggressive surgical intervention, a trend which is particularly high in young Caucasian women.^1,5 Understanding what motivates women to make this decision will help guide physicians in how they counsel patients. Women who are accurately informed, and who have a better understanding of risk and overestimation, will be better positioned to make appropriate treatment decisions.