Are diabetes and breast cancer linked?

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Carol Sorgen

The link between obesity and adult-onset diabetes has been well-documented in studies. Now researchers are investigating the relationship between the high insulin levels that can accompany obesity and/or diabetes and the risk of breast cancer.

Mercy Medical Center in Baltimore is participating in a National Cancer Institute-funded study to research the link between insulin resistance and breast cancer prognosis in African American and Caucasian women.

The role of insulin

Insulin helps the body make use of the glucose (blood sugar) that results from digesting food. Insulin resistance means the body needs high levels of insulin to respond properly to the food we eat.

According to Dr. Nina Bickell, co-director of the Center for Health Equity & Community Engaged Research at the Icahn School of Medicine at Mount Sinai Hospital in New York City, African American women are more likely to suffer from obesity, and obesity often goes hand in hand with insulin resistance. In addition, she said, African American women tend to get more aggressive forms of breast cancer and have higher mortality rates from the disease. 

The study taking place at Mercy seeks to determine whether racial differences in insulin resistance are responsible for more aggressive breast cancers, which may explain some of the higher mortality rates African American women with breast cancer experience.

In a study published last year in the journal Cancer Research, researchers reported on insulin’s role in breast cancer risk. More than 3,300 women without diabetes were studied; 497 of them developed breast cancer over the course of eight years.

The study showed that high fasting insulin levels doubled the risk of breast cancer, both for overweight and normal-weight women. In addition, women who were overweight and insulin-resistant were 84 percent more likely to develop breast cancer than overweight women who weren’t insulin-resistant.

Because of Baltimore’s significant African American population, Dr. Neil Friedman, director of the Hoffberger Breast Center at Mercy Hospital and principal investigator of the study there, believes that the Mount Sinai study can prove useful in developing prevention and treatment options.

Taking part in the study

The study will evaluate 1,286 participants in six hospitals through November 2017. Mercy is the only hospital in Maryland participating in the study.

Participants should be African American or Caucasian women with a diagnosis of new invasive breast cancer, who are not taking medication for diabetes, and who have not yet begun active breast cancer treatment.

Those who are approved for the study will make one visit to Mercy Hospital. They will take part in a brief survey, have measurements such as weight and height taken, and provide blood and tissue samples, which are taken during breast cancer surgery. Each participant will receive a gift card as a thank you for taking part in the study.

Taking part in the study does not affect treatment. Information gathered will be used for the development of future prevention and treatment plans.

For more information, or to volunteer to participate, call (410) 332-9330 or (410) 951-7950 or visit