Type II Diabetes and Incidence of Estrogen Receptor Negative Breast Cancer in African American Women

Authors: Palmer, J.R. et al.

Source: Cancer Res 77(22) November 15, 2017

www.ncbi.nlm.nih.gov/pubmed/29141994

Women with T2D have an approximately 20% increased risk of breast cancer. The role of diabetes in breast cancer has been studied for several years now. There are many theories to explain the associations between the two diseases, including the presence of insulin-like growth factor as well as the presence of a pro-inflammatory state. The prevalence of T2D is twice as high among African American women as white women. The investigators questioned if T2D was responsible for increasing breast cancer risk in African American women.

The Black Women’s Health Study began in 1995 as a questionnaire for 59,000 African American women across the nation. Every two years, participants are sent new questionnaires to provide updates on their health status, including new diagnoses of breast cancer and T2D, as well as current weight. The current study used the most recent information from these questionnaires to try to draw conclusions about diabetes and breast health within this population.

There was a positive association between T2D and the rate of ER- breast cancer. Women with T2D had a 40% greater risk of acquiring the disease compared to women without T2D. Interestingly, this greater risk was only seen among premenopausal women. Also, T2D was not associated with an increased risk of developing estrogen receptor positive breast cancer.

Diabetes is often associated with obesity, and the rate of obesity is highest among African American women compared to other ethnic groups. The investigators looked into the rate of obesity among the study participants to see if obesity, and not T2D, was the cause for the increased rate of cancer. When they controlled for body mass index,  T2D was associated with a greater rate of ER- disease for women who were not obese. There was no increased cancer risk with T2D among obese women.

These findings suggest that the metabolic changes of T2D in non-obese African American women may be associated with ER- breast cancer. There may be a connection between the increased rates of both diseases in this group of women. This information provides another reason for emphasizing the detection and successful control of T2D among African American women. Moreover, there may be opportunity to reduce breast cancer risk with the use of certain T2D medications.