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Cancer Causes Control. 2017 Jan;28(1):61-67. doi: 10.1007/s10552-016-0837-z. Epub 2016 Dec 19.

Diabetes and breast cancer mortality in Black women.

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Section of Hematology and Oncology, Department of Medicine, Evans Biomed Research Center, Boston University School of Medicine, 650 Albany Street, Suite 406, Boston, MA, 02118, USA.
Slone Epidemiology Center, Boston University, Boston, MA, USA.
Naval Health Research Center, Henry M. Jackson Foundation for the Advancement of Military Medicine, San Diego, CA, USA.
Departments of Medicine and Pharmacology, BU-BMC Cancer Center, Boston University School of Medicine, Boston, MA, USA.
Cancer Prevention and Control, Georgetown Lombardi Comprehensive Cancer Center, Washington, DC, USA.



Breast cancer mortality is higher in Black women than in White women. The prevalence of type 2 diabetes mellitus is also higher, yet data on whether diabetes affects breast cancer mortality in this population are lacking. We investigated the relation of diabetes at the time of breast cancer diagnosis to breast cancer mortality in the Black Women's Health Study, a prospective cohort study.


1,621 Black women with invasive breast cancer diagnosed in 1995-2013 were followed by mailed questionnaires and searches of the National Death Index. Multivariable Cox regression analysis was used to compute hazard ratios (HRs) for diabetes in relation to breast cancer mortality and all-cause mortality, with adjustment for age, stage, treatment modality, estrogen receptor (ER) status, and body mass index.


There were 368 deaths during follow-up, of which 273 were due to breast cancer. Breast cancer mortality was significantly increased in women who had been diagnosed with diabetes at least 5 years before breast cancer occurrence, HR 1.86 (95% CI 1.20-2.89), with elevations observed for both ER+ and ER- breast cancer. All-cause mortality was also higher in diabetics, with HRs of 1.54 (95% CI 1.12-2.07) overall and 2.26 (95% CI 1.62-3.15) for ≥5-year duration of diabetes relative to non-diabetics.


Our results present the first solid evidence of a positive association of type 2 diabetes with breast cancer mortality in Black women. Given the higher prevalence and earlier onset of type 2 diabetes in Black women, it is likely that diabetes contributes to racial disparities in breast cancer mortality.


Black women; Breast cancer; Diabetes; Mortality

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