A synthetic form of insulin has been linked to an increased risk of cancer, studies in Europe indicate, but doctors caution that the findings are preliminary and may not hold up under greater scrutiny.
The drug, which goes by the brand name Lantus and is marketed by Sanofi-Aventis, provides a once-daily injection of artificial insulin.
For many diabetes patients who depend on insulin to regulate blood sugar, the once-a-day therapy has been hailed as a benefit over other drugs that require more frequent injections.
But studies in Europe are casting a pall over the treatment. An analysis of data from 127,000 insulin patients in Germany found an increased risk of colon cancer among those who used Lantus, particularly among patients who took a higher dose of the drug.
A second, smaller study in Sweden found a similar increased risk for breast cancer, but two other studies found no statistically signficant link between the diabetes drug and cancer. The findings are published in the journal Diabetologia (http://www.diabetologia-journal.org)
Dr. John Buse, director of the Diabetes Care Center at the UNC-Chapel Hill School of Medicine and past president of the American Diabetes Association, said insulin-dependent patients should not panic about the suggested link.
"Don't stop taking insulin," Buse said. "If it makes you nervous, talk to your doctor about switching to a different kind of insulin."
Buse said most patients have nothing to fear from taking Lantus, but he said patients who have had cancer, and those who have a family history of the disease, might consider switching to another form of insulin.
Buse said more research is needed before a definitive link can be made between Lantus and cancer. He said the European studies may have been biased to include patients who were screened more actively for cancers.
A long-term study in the United States is currently underway that may be able to confirm or disprove the cancer link. That study is not expected to be complete for years, however.