Diabetes Linked to Breast Cancer Risk in African American Women

A diagnosis of type 2 diabetes may carry an increased risk of developing breast cancer among African American women, according to a study published by Cancer.

Recent evidence suggests that the risk of estrogen receptor positive (ER+) and estrogen receptor negative (ER-) breast cancer may be driven by different factors. The study authors focused on determining whether diabetes may be linked to the breast cancer subtypes.

Included in the analysis were data from 54,337 African American women participating in the Black Women’s Health Study. All patients were cancer-free at baseline and were followed for 18 years. During follow-up, there were 914 cases of ER+ breast cancer and 468 cases of ER- breast cancer.

Notably, the authors discovered that African American women with type 2 diabetes had a 43% increased risk of developing ER- breast cancer compared with patients without diabetes, according to the study.

However, the authors did not discover an increased risk of ER+ breast cancer among patients with diabetes compared to those without. This finding was not linked to obesity status, according to the authors.

“While we observed no association for the most common type of breast cancer, the type that is responsive to estrogens, diabetic women were estimated to be at increased risk of developing estrogen receptor negative breast cancer, a more aggressive type of breast cancer which is twice as common in US black women as in white women,” said corresponding author Julie Palmer, ScD.

The authors hypothesize that the risk of ER- breast cancer may be increased due to chronic inflammation from diabetes, which is thought to promote cancer.

“Given that the prevalence of diabetes is twice as high in African Americans as in whites, the current finding, if confirmed, may help to explain the higher incidence of ER- breast cancer in African American women,” Dr Palmer said. “Inflammation is thought to play a bigger role in ER-negative breast cancer, and women with type 2 diabetes generally have higher levels of circulating inflammatory factors which can cause more inflammation in the tumor microenvironment, contributing to growth of cancers.”

The authors caution that these findings are preliminary and additional studies must be done to confirm this link; however, if proven, preventing diabetes may be even more important than previously thought.

“If these results are confirmed, type 2 diabetes would be a modifiable risk factor for ER-negative breast cancer,” Dr Palmer said. “Women could reduce their chances of getting ER-negative breast cancer by reducing their likelihood of getting type 2 diabetes. This would be yet another reason to treat diabetes early.”