FINDINGS from a recent study have cast doubt on the long-term mortality benefits of bilateral mastectomy for women with unilateral breast cancer. A large cohort study analysed data from the Surveillance, Epidemiology, and End Results (SEER) Program to estimate the 20-year cumulative risk of breast cancer mortality among women with stage 0 to stage III unilateral breast cancer.
The study involved 661,270 women diagnosed with unilateral breast cancer, including both invasive and ductal carcinoma in situ, between 2000 and 2019. These women were closely matched by the type of initial surgery they received—lumpectomy, unilateral mastectomy, or bilateral mastectomy—and followed for two decades.
The findings revealed that bilateral mastectomy was associated with a lower incidence of contralateral breast cancer. Specifically, out of 36,028 women in each treatment group, there were 766 contralateral breast cancers in the lumpectomy group, 728 in the unilateral mastectomy group, and only 97 in the bilateral mastectomy group. This translates to a 20-year risk of contralateral breast cancer of 6.9% for the lumpectomy-unilateral mastectomy group.
However, the reduction in contralateral breast cancer did not correlate with a decrease in breast cancer mortality. Data found that the cumulative mortality from breast cancer at 15 years was 32.1% for those who developed contralateral cancer compared to 14.5% for those who did not. The overall breast cancer mortality rates were 8.54% in the lumpectomy group, 9.07% in the unilateral mastectomy group, and 8.50% in the bilateral mastectomy group.
These results suggest that while bilateral mastectomy y significantly reduces the risk of developing cancer in the opposite breast, it does not confer a survival advantage over lumpectomy or unilateral mastectomy over 20 years. The study’s authors from the Institute of Diabetes Research in Munich emphasise the need for further research to understand why reducing the risk of contralateral breast cancer does not translate into lower overall breast cancer mortality. They also note the importance of considering these findings in the context of patient decisions about surgical treatment options for unilateral breast cancer.
Laith Gergi, EMJ
Reference
Giannakeas V et al. Bilateral mastectomy and breast cancer mortality. JAMA Oncol. 2024; DOI:10.1001/jamaoncol.2024.2212.
