Is Contralateral Mastectomy Effective?
Does bilateral mastectomy for treatment of unilateral breast cancer reduce the 20-year risk of breast cancer mortality? A recent study has tried to answer this question. The study included 661,270 women (about half the population of Hawaii) with unilateral stage 0-III breast cancer who were closely matched by treatment type (lumpectomy, unilateral mastectomy, or bilateral mastectomy) and followed up for 20 years.
The findings indicate that contralateral mastectomy for unilateral breast cancer is an effective means of cancer prevention but does not reduce the risk of dying of breast cancer. This cohort study used the Surveillance, Epidemiology, and End Results (SEER) Program registry database to identify women with unilateral breast cancer who were diagnosed from 2000 to 2019.
During the 20-year follow-up, there were 766 contralateral breast cancers observed in the lumpectomy group, and 728 contralateral breast cancers in the unilateral mastectomy group. The cumulative breast cancer mortality was 32.1% at 15 years after developing a contralateral cancer and was 14.5% for those who did not develop a contralateral cancer. Deaths from breast cancer totaled 3,077 women (8.54%) in the lumpectomy group, 3,269 women (9.07%) in the unilateral mastectomy group, and 3,062 women (8.50%) in the bilateral mastectomy group.
This cohort study indicates that the risk of dying of breast cancer substantially increases after experiencing a contralateral breast cancer. Women with breast cancer treated with bilateral mastectomy had a greatly diminished risk of contralateral breast cancer; however, they experienced similar mortality rates as patients treated with lumpectomy or unilateral mastectomy.
Once again, the value of our cancer registries and the importance of aggressive patient follow-up have been shown to answer important oncological questions.
