Cancer-Diabetes Link Is Explored
Diabetes, particularly type 2, is associated with an increased risk of cancers of the liver, pancreas, endometrium, colon, rectum, breast, and bladder, according to a joint consensus statement by the American Diabetes Association and the American Cancer Society.
The panel of experts that drafted the statement also found a decreased risk of prostate cancer in people with diabetes. For other cancers, there was either no association or insufficient data to draw conclusions.
Though associations were found, there isn't enough evidence to say whether diabetes causes cancer nor is it clear why it might. Several risk factors are common to diabetes and cancer, including aging, obesity, poor diet, smoking, and physical inactivity, which may be why the two diseases are more likely to be found together. Yet it's also possible that diabetes could cause cancer. Diabetes-associated inflammation, high blood glucose, or too much insulin in the body may all promote tumor growth.
Another potential link between cancer and diabetes is medication. Though some evidence suggests that the diabetes medication metformin may be protective against cancer, other data hint that insulin treatment, particularly with insulin glargine (Lantus), may raise cancer risk. More research is needed, the authors say, and cancer risk should not influence treatment choices for most people with diabetes, though careful consideration may be necessary for people at very high risk for cancer (or for recurrence of specific cancers).
Many questions remain for researchers. "Traditionally, there hasn't been much overlap between research in cancer and in diabetes," says Edward Giovannucci, MD, SCD, cochair of the consensus report group. "Our summary may raise more questions than provide answers, but we hope that it will spur additional studies."
Even so, there is compelling evidence that maintaining a healthy weight, diet, and exercise routine can guard against type 2 diabetes and some forms of cancer. Given the association between diabetes and some cancers, the authors urge all people with diabetes to get cancer screenings as recommended for people of their age and sex.