Many women diagnosed with breast cancer in one breast opt for a double mastectomy to prevent the cancer from spreading to the other breast, but a new study finds that doing so doesn’t actually improve their survival rate.
The study, published July 25 in JAMA Oncology, analyzed more than 661,000 women diagnosed with cancer in one breast between 2000 and 2019. Cases ranged from ductal carcinoma in situ, a noninvasive stage 0 breast cancer, to invasive stage 3 breast cancer.
Women who had a lumpectomy or mastectomy had only a 7% chance of later developing cancer in the other breast. The researchers also found that removing the other breast during a double mastectomy offered no survival advantage.
Over the 20-year period studied, breast cancer death rates were similar in all groups: 8.5% for women who underwent lumpectomy, 9% for women who underwent mastectomy, and 8.5% for women who underwent bilateral mastectomy.
“It seems like a paradox,” said lead author Dr. Steven Narod, a breast cancer researcher and physician at Women’s College Hospital in Toronto. “If you get contralateral breast cancer, you’re at increased risk of dying, but preventing it doesn’t improve survival.”
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Narod said the study raises important questions about contralateral breast cancer – an invasive second breast cancer that occurs more than six months after the first breast cancer is diagnosed – and how breast cancer spreads.
Additionally, the study notes that these results may not apply to people who test positive for the BRCA gene and are at greater risk. According to the CDC, one in 500 women in the U.S. has the genetic mutation. In these cases, the researchers and the American Cancer Society say that a double mastectomy performed as a preventive surgery is worth considering.
One in eight women in the United States will be diagnosed with breast cancer, making mammograms essential for early detection.
In May 2023, the U.S. Preventive Services Task Force lowered the recommended age for breast cancer screening in response to an increase in breast cancer diagnoses at younger ages. The task force said science now shows that all women should be screened every two years starting at age 40, which could increase the number of lives saved by 19%.
In addition to sticking to regular exams, health officials encourage women of all ages to practice “breast self-awareness,” which means being familiar with what your breasts normally look and feel like so you’re more likely to spot any abnormalities when performing a breast self-exam.
