Diabetics urged to stay on popular insulin Lantus

CHICAGO (Reuters) - Dr. Louis Philipson has already started fielding calls from worried diabetics after new studies of 300,000 patients released on Friday suggested the Sanofi-Aventis insulin drug Lantus might raise the risk of cancer.

"I think the deluge is about to hit," Philipson, of the University of Chicago Medical Center, said in a telephone interview.

Diabetes experts are cautioning patients to keep taking Lantus, an artificial form of insulin called an insulin analog that is used by millions of people with type 1 and type 2 diabetes to control their blood sugar. The drug, known generically as glargine insulin, had sales of $3.43 billion last year.

Four studies released in the journal Diabetologia raised concerns about the drug, but the results were conflicting.

"This not an emergency. This is just a question we have to answer now," said Dr. R. Paul Robertson, president of the American Diabetes Association and a diabetes researcher at the University of Washington in Seattle.

"The major thing is people should continue taking their insulin," Robertson said in a telephone interview.

Lantus is typically taken just once a day. It has been widely used since 2000.

Unlike human insulin, a hormone normally produced by the pancreas that helps the body use glucose for energy, Lantus has a slightly altered molecular structure that allows it to last longer in the body.

"It's frequently prescribed in the United States. When I have patients with type 1 or type 2 diabetes, I give that drug. It's been very effective," Robertson said.

All people with type 1 diabetes need to take insulin to survive; many patients with type 2 diabetes also need to take insulin to control their blood glucose.

Robertson said it is not clear if the same problems would be seen in Levemir, another long-acting insulin analog made by Denmark's Novo Nordisk.

"Lantus has been out there longer. Other drugs haven't had time to show they have the same kind of effects," he said.

The American Diabetes Association has recommended that patients continue on the treatment, and consult their doctor before making any changes.

Philipson said insulin is a type of compound called a growth factor and prior studies have shown that when insulin is added to cells in a cell culture, it makes them grow.

"That would also include tumor cells," he said.

Philipson said it may be that patients taking Lantus are simply exposed to insulin longer, and if they have any underlying tumors, the drug may accelerate tumor growth.

"Even though this information is early and the results are conflicting, it's still the case that using less of this drug is a good idea," he said.

He said patients with type 2 diabetes should use diet and exercise to improve their body's ability to use insulin, which may allow them to use less artificial insulin.

(Editing by Maggie Fox, Bernard Orr)