Breast cancer and diabetes deadly combination, finds review

Kathleen Blanchard's picture

Women with diabetes and breast cancer are twice as likely to die from any cause.

The findings have important implications for understanding whether high blood sugar levels affect tumor growth. Johns Hopkins researchers discovered the link that they say should be further explored to find out what factors contribute to higher rates of death for women with breast cancer and diabetes.

Study leader Kimberly S. Peairs, M.D., an assistant professor of medicine at the Johns Hopkins University School of Medicine explains, “When patients are faced with a diagnosis of breast cancer, which they see as an imminent threat to their lives, diabetes care often goes on the back burner.” The findings from the scientists suggest poor blood sugar control might play a role that leads to higher risk of dying for diabetic women with breast cancer.

“This research suggests we may need to proactively treat the diabetes as well as the cancer,” adds Dr. Peairs. The researchers found the combination of breast cancer and diabetes could be deadly in an in-depth review of eight studies on diabetes and breast cancer.


In six out of seven studies, the investigators found women with preexisting diabetes had higher rates of death from all causes, leading the scientists to believe diabetes poses unknown dangers, especially in the presence of breast cancer.

Dr. Peairs says it may be that women with diabetes receive less aggressive treatment for breast cancer from fears chemotherapy and radiation will lead to more side effects, such as hospitalization and infection. Other possible reasons for the higher death rates associated with breast cancer in combination with diabetes include poor health in general. Diabetes is associated with other risk factors such as high cholesterol, obesity and hypertension.

There are also questions about whether diabetes drugs help or harm breast cancer patients that need further study. An example cited by Peairs is the drug metformin that actually might improve breast cancer survival.

Given the high incidence of both diabetes and breast cancer, the authors suggest more research to understand why women with breast cancer and diabetes are more likely to die, found in the review.

JCO Jan 1, 2011:40-46; DOI:10.1200/JCO.2009.27.3011.
"Diabetes Mellitus and Breast Cancer Outcomes: A Systematic Review and Meta-Analysis"