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July 2, 2009 -- Shaky data from European studies suggest that the long-acting insulin product Lantus might slightly increase cancer risk in people with type 2 diabetes.
People should not stop taking Lantus because of this finding, says the FDA. A wide range of diabetes organizations -- and the editors of the journal that published the new findings -- agree that there's no cause for alarm.
"Do not stop taking your insulin. There is no immediate danger if you currently use or previously used ," says the American Diabetes Association.
"The FDA recommends that patients should not stop taking their insulin therapy without consulting a physician. Patients should contact their health care professional if they have concerns about the medicines they are taking," says the FDA.
So what's all the buzz about?
Insulin is a hormone that has effects throughout the body. One of those effects is to stimulate cell growth. There's evidence from animal studies that insulin, particularly long-acting insulin, may cause existing cancer cells to grow faster.
A German research team wondered whether there's any evidence this happens in humans. They analyzed medical records from a large number of people enrolled in an insurance plan. People taking Lantus did not have more cancers than people taking other forms of insulin.
But people on Lantus took lower doses of insulin than other insulin users. When the German researchers adjusted their data to account for dosage, a link between Lantus and cancer risk appeared.
When the researchers submitted their study to Diabetologia, the journal of the European Association for the Study of Diabetes (EASD), the journal asked them to wait until new studies could be done to confirm or refute the finding. So three new studies -- one in Sweden, one in Scotland, and one in the U.K. -- took a look.
In the Swedish and Scottish studies, there was no increased cancer risk in patients who took Lantus along with other forms of insulin. But among women who took Lantus alone in the Swedish study, there was a higher risk of breast cancer -- about one or two extra cases per 1,000 women treated for one year. The Scottish study found a similar trend.
Because patients taking Lantus alone in these studies were older and had other factors linked to cancer, the studies are inconclusive. The researchers who conducted the studies are quick to point out that their findings do not prove a link between Lantus and cancer.
The U.K. study found no link between Lantus and cancer. But it did turn up some interesting good news: People taking the oral ?diabetes drug metformin had less cancer than those who did not use metformin, whether or not they were taking Lantus or other insulins.
Sanofi-aventis, which makes Lantus, says the company "confirms the safety of Lantus."
"Patient safety is the primary concern of Sanofi-aventis," they company says in a written statement provided to WebMD. "Sanofi-aventis will continue to vigorously monitor the safety of Lantus and is committed to working with the FDA and other regulatory agencies as well as other scientific experts to clarify this situation."
The FDA and EASD are conferring with Sanofi-aventis to discuss how to perform studies that will provide more definitive data.