Here’s what’s really interesting: The association was observed only among women with BMIs under 30, which could mean that abnormal metabolic status may play a larger role in ER-negative breast cancer than obesity.
The results showed an increased risk of ER-negative breast cancer primarily in black women who had type 2 diabetes for at least five years. Researchers found no association with ER-positive breast cancer in the same group.
African-American women who get breast cancer are more likely to get TNBC than white women, with double the incidence as compared to white women, according to the paper’s author, Julie R. Palmer, ScD, associate director of Boston University’s Slone Epidemiology Center. And type 2 diabetes is also twice as prevalent in African-American women.
“We are still trying to understand the basic biological processes that lead to ER-negative breast cancer. One way to do this is to study factors that are more common in an African-American population,” she said. Several studies suggest that diabetes is a risk factor for breast cancer and insulin resistance is a factor in TNBC.
The study was based on information provided by participants in the Black Women’s Health Study (BWHS, which uses twice-yearly questionnaires from 59,000 African- American women from across the United States.
“Our findings may account for some of the racial disparity in breast cancer, and could partly explain why mortality from breast cancer is so much higher in black women than white women,” Palmer said. “Women could reduce their chances of getting ER-negative breast cancer if they could avoid developing type 2 diabetes. Monitoring of blood sugar levels to identify pre-diabetes may allow for early interventions to prevent diabetes.”
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