Bilateral Mastectomy May Not Increase Survival Compared to Breast-Conserving Surgery With Radiation in Women With Unilateral Breast Cancer

EBM Focus - Volume 9, Issue 36

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Reference: JAMA 2014 Sep 3;312(9):902 (level 2 [mid-level] evidence)

Bilateral mastectomy rates have been on the rise among women with early breast cancer in recent years (J Clin Oncol 2009 Sep 1;27(25):4-82, J Clin Oncol 2011 Jun 1;29(16):2158). However, while bilateral mastectomy has been shown to reduce the incidence of breast cancer in women at increased risk (Ann Oncol 2013 Aug;24(8):2029 full-text), the evidence is inconsistent for bilateral mastectomy as a treatment in women with unilateral breast cancer (Cochrane Database Syst Rev 2010 Nov 10;(11):CD002748). Furthermore, no randomized trials have been performed comparing bilateral mastectomy vs. breast-conserving surgery plus radiation. Many women with breast cancer have a preference for bilateral mastectomy based on its perceived benefits, and may object to randomization to less extensive surgery, making it difficult to conduct randomized trials for this particular comparison. A new population-based cohort study evaluated bilateral mastectomy, unilateral mastectomy, and breast-conserving surgery with radiation in 189,734 women with early (stage 0-III) unilateral breast cancer using data collected from 1998 to 2011 in the California Cancer Registry.

A total of 6.2% of women had bilateral mastectomy, 38.8% had unilateral mastectomy, and 55% had breast-conserving surgery with radiation. The overall rate of bilateral mastectomy increased during the study, ranging from 2% in 1998 to 12.3% in 2011. Factors most significantly associated with increased rate of bilateral mastectomy vs. breast-conserving surgery with radiation included age < 50 years, positive lymph node status, and lobular histology. However, data on other relevant information that may have influenced a treatment decision (such as magnetic resonance imaging or BRCA1 or BRCA2 gene mutation status) were not available from the registry.

There were no significant differences in the all-cause or breast cancer-specific mortality comparing bilateral mastectomy vs. breast-conserving surgery with radiation. Both approaches were associated with small but significant reductions in mortality compared to unilateral mastectomy. Estimated 10-year all-cause mortality was 16.8% with breast-conserving surgery with radiation, 18.8% with bilateral mastectomy, and 20.1% with unilateral mastectomy.

This study supports the use of breast-conserving surgery with radiation as the first line of treatment for women with early stage unilateral breast cancer. However, the lack of information on potential confounders, such as magnetic resonance imaging or gene mutation results, detailed patient history, and physician recommendations limit the ability to make definitive conclusions from the current data.

For more information see the Surgery for early and locally advanced breast cancer topic in DynaMed.