A series of European studies reached conflicting conclusions about a potential link between cancer and the long-acting insulin glargine (Lantus). One study reported a higher cancer rate with insulin glargine, but only at higher doses. Another study showed an increased rate of breast cancer with glargine alone compared with insulins other than glargine. However, using insulin glargine in combination with other insulins was not associated with an increased cancer rate. Two other studies concluded that the use of glargine did not raise cancer risk relative to other insulin therapies. Insulin glargine, an artificial form of human insulin that is typically administered once a day, has been widely used since 2000.

Because of the nature of the studies, other factors that might have influenced cancer rates—like excess body weight, insulin dose, duration of diabetes, or the presence of other illnesses—could often not be accounted for. Therefore, the cause of the increase in reported cancers is unknown, and additional studies will be needed to settle the matter. In the meantime, the American Diabetes Association and a number of other agencies and experts agree that there is no conclusive evidence linking the use of insulin glargine or any other insulin to the development of cancer. People with diabetes are urged to continue taking their prescribed insulin.
Source: Diabetologia, published online June 26, 2009

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