FDA warns that Lantus diabetes insulin could lead to cancer risk
The FDA has notified healthcare professionals and patients that it is aware of four recently published observational studies that looked at the use of Lantus (insulin glargine injection) diabetes therapy, and its possible risk for cancer in patients with diabetes.

Three of the four studies suggest an increased risk for cancer associated with use of Lantus from sanofi-aventis U.S., according to the agency. Based on the currently available data, the FDA is recommending that patients should not stop taking their insulin therapy without consulting a physician, since uncontrolled blood sugar levels can have both immediate and long-term serious adverse effects. 

Insulin glargine is used to control blood sugar in people with type 1 and type 2 diabetes.  Insulin glargine, however, is a modified version of human insulin that allows for the control of blood sugar for extended periods of time. Insulin glargine is approved for once-a-day dosage by subcutaneous injection.

However, the FDA said it is currently reviewing many sources of safety data for Lantus, including the "newly published observational studies, data from all completed controlled clinical trials, and information about ongoing controlled clinical trials, to better understand the risk, if any, for cancer associated with use of Lantus."

The four observational studies (see here) evaluated large patient databases and all reported some level of association between the use of insulin glargine, and other insulin products, and various types of cancer. The duration of patient follow-up in all four studies was shorter than what is generally considered necessary to evaluate for cancer risk from drug exposure.

Further, inconsistencies in findings within and across individual studies raise concerns as to whether an association between the use of insulin glargine and cancer truly exists.  Additionally, differences in patient characteristics across the treatment groups may have contributed to a finding of increased cancer risk, the FDA noted. 

Finally, the agency said it is currently in discussions with sanofi-aventis, as to whether any additional studies evaluating the safety and efficacy of this drug will need to be performed.