Risk of Contralateral Breast Cancer Lower With Bilateral Mastectomy

MONDAY, July 29, 2024 (HealthDay News) -- For women with unilateral breast cancer, the risk of contralateral breast cancer is lower after bilateral mastectomy, but mortality rates are similar to those after lumpectomy or unilateral mastectomy, according to a study published online July 25 in JAMA Oncology.

Vasily Giannakeas, Ph.D., M.P.H., from the Women's College Hospital in Toronto, and colleagues used the Surveillance, Epidemiology, and End Results Program registry database to identify women with unilateral breast cancer who were diagnosed from 2000 to 2019. Three matched cohorts were generated according to surgical approach. The cohorts were followed for contralateral breast cancer and breast cancer mortality for up to 20 years.

The study sample included 661,270 women; after matching, 36,028 women were included in the three treatment groups. The researchers identified 766, 728, and 97 contralateral breast cancers in the lumpectomy group, the unilateral mastectomy group, and the bilateral mastectomy group, respectively. In the lumpectomy-unilateral mastectomy group, the 20-year risk of contralateral breast cancer was 6.9 percent. The cumulative breast cancer mortality was 32.1 and 14.5 percent at 15 years after developing a contralateral cancer and among those who did not develop contralateral cancer, respectively (hazard ratio, 4.00). Overall, deaths from breast cancer occurred in 8.54, 9.07, and 8.50 percent of women in the lumpectomy, unilateral mastectomy, and bilateral mastectomy groups, respectively.

"Women with unilateral breast cancer should be advised that bilateral mastectomy greatly reduces the risk of a second cancer, but does not affect mortality," the authors write.

One author disclosed ties to the pharmaceutical industry.

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