Type 2 Can Increase Risk
After 20 years of living with type 2 diabetes and a long struggle with her weight, Leila Berner got the diagnosis everyone fears: cancer. Leila, a 63-year-old rabbi who lives near Washington, D.C., never connected her diabetes and breast cancer until her doctors advised that she lose weight and get active for long-term survival. She also underwent a lumpectomy, radiation, and chemotherapy following her 2010 diagnosis.
Diabetes and cancer are close cousins, and diabetes is often the first to show up. Researchers have amassed a large knowledge base on the link between diabetes and cancer, says Lesley Fels Tinker, Ph.D., RD, principal staff scientist at Fred Hutchinson Cancer Research Center in Seattle. Though questions remain, experts are sure there are several things you can do today to reduce your cancer risks.
According to a 2010 consensus report published jointly by the American Diabetes Association (ADA) and the American Cancer Society (ACS), the risk of a person with type 2 diabetes developing cancer is 20-50 percent higher than a person without diabetes. Research also indicates that people with type 2 diabetes who develop cancer may experience a shorter life expectancy. That's mainly because of their existing risk or presence of heart disease and/or because many cancer treatments can harm the heart and circulatory system. Being overweight increases the odds of cancer reoccurrence. With diabetes and cancer on the rise and already the second and seventh leading causes, respectively, of death in the United States, health experts are sounding the alarm.
How are cancer and diabetes related?
"When people gain excess weight, they unlock a cascade of metabolic changes that, over years, can lead to insulin resistance, chronic inflammation, high levels of circulating insulin, and years later -- if not reversed or treated -- elevated blood glucose levels high enough to diagnose type 2," says Derek LeRoith, M.D., Ph.D., professor of medicine and endocrinology at the Icahn School of Medicine at Mount Sinai in New York City.
Experts now theorize that high insulin levels increase the growth of cancer cells, which in turn stimulate the formation of new blood vessels. The vessels then provide nourishment to cancerous tumors. Overweight people also have lower levels of adiponectin, a hormone secreted by adipose tissue (fat), than lean people, which may further accelerate cancer growth.
"It's like a double whammy for people with prediabetes or type 2 diabetes, and for the most part, you're totally unaware this is happening," Tinker says.
As Karen Collins, RD, a nutrition adviser to the American Institute for Cancer Research (AICR), says: "People don't realize the extra pounds they carry around aren't inert blobs of fat, like pounds of butter or plastic fat models we use as visual aids." The adipose tissue is busy at work doing its devilish damage -- and the more adipose tissue you have, the more damage is being done.
To add insult to injury, one or more of the blood glucose-lowering medications you take may increase your risk of developing cancer. Derek LeRoith, M.D., Ph.D., says cancer risk, history of cancer, and tolerance of and need for medications are all things that should be considered when selecting glucose-lowering medications. There is, however, "insufficient evidence" to warrant withholding certain glucose-lowering medications on the basis of cancer concerns, according to a joint consensus statement of the American Association of Clinical Endocrinologists and the American College of Endocrinology released in late August.
"For most people with diabetes, the benefits of treatment should take precedence over concerns for potential low-grade cancer risk until more definitive evidence becomes available," the statement says.
Cancers linked to diabetes
People with diabetes experience a higher prevalence of these cancers:
- Breast cancer in women (postmenopausal)
- Endometrial (the lining of the uterus in women)
Pancreatic (thought to be a risk factor for diabetes)