Risk of cancer in patients receiving insulin glargine

The risk of malignancy in patients using insulin glargine was evaluated. Patients with diabetes mellitus have increased rates of cancers including breast, colon, and pancreatic cancers. Since nondiabetic patients with increased levels of insulin have similar rates of the same cancers, hyperinsulinemia could be key. Normally, insulin produces metabolic effects and insulin-like growth factor-I (IGF-I) produces mitogenic effects. Since the molecules are structurally similar, it is possible for insulin to act like IGF-I, promoting mitogenicity. Concern that insulin may promote the growth of some cancers is heightened with insulin analogues, since changing the structure of human insulin could produce molecules with increased mitogenic potential. In vivo, insulin glargine has been shown to have greater mitogenic potential than human insulin. It is unknown whether this occurs in vitro, because the insulin glargine molecule is transformed once injected. Studies published in 2009 suggest that patients on insulin glargine could be at greater risk for cancer than patients on other antidiabetes therapies, but the trial results are conflicting. In response, the Food and Drug Administration, American Diabetes Association, American Association of Clinical Endocrinologists, and European Association for the Study of Diabetes have formally stated that patients should continue to use insulin glargine until more information is available. Studies on the relationship between insulin glargine and cancer have been inconclusive.