A new study published in the Journal of the American Medical Association shows that while contralateral mastectomy is an effective preventive measure for unilateral breast cancer, it does not reduce the risk of breast cancer-related death or raise concerns about a new cancer in the opposite breast spreading.
Many women with unilateral breast cancer opt for bilateral mastectomy, believing it to be the best way to prevent a second tumor and reduce mortality. However, this study found that while removing a healthy breast lowers the chance of developing another breast cancer, it does not reduce breast cancer death rates. Led by Vasily Giannakeas, the study aimed to calculate the 20-year risk of breast cancer mortality for women with stage 0 to stage III unilateral breast cancer, based on the type of surgery performed.
The researchers analyzed women diagnosed with invasive or ductal carcinoma in situ between 2000 and 2019 using the SEER database. They created three closely matched cohorts based on surgical treatment (lumpectomy, unilateral mastectomy, bilateral mastectomy) and monitored breast cancer mortality and contralateral breast cancer risk over 20 years.
As reported by medicaldialogues, the study included 661,270 women, with around 36,028 in each treatment group after matching. Over the 20-year follow-up, there were 766 contralateral breast cancers in the lumpectomy group, 728 in the unilateral mastectomy group, and 97 in the bilateral mastectomy group. The 20-year risk of contralateral breast cancer in the lumpectomy-unilateral mastectomy group was 6.9%.
After 15 years, the cumulative breast cancer mortality rate was 32.1% for those who developed contralateral cancer, compared to 14.5% for those who did not. Breast cancer deaths were similar across the groups: 37 women in the lumpectomy group, 36 in the unilateral mastectomy group, and 36 in the bilateral mastectomy group.
Although bilateral mastectomy reduced the risk of contralateral breast cancer, the study found no difference in breast cancer mortality between the three surgical treatments.