Lantus Insulin Side Effects Linked to Risk of Cancer: Study

New research suggests that side effects of Lantus, an artificial form of insulin manufactured by Sanofi-Aventis for diabetes, may increase the risk of developing cancer.

The report, published in the medical journal Diabetologia, found that in studies in Germany and Sweden, there was an increase in the incidence of cancer among diabetics using Lantus insulin. However, editors of the journal and the European Association for the Study of Diabetes (EASD) caution that the results are inconclusive and that more in-depth studies need to be done about the potential Lantus cancer risk.

Lantus (glargine) is an injection taken once per day, which slowly releases insulin into the blood over time. It has the second largest share of the diabetic drug treatment market and brought in $3.45 billion in worldwide sales last year. The drug was approved by FDA for diabetes treatment in 2000.

The new report looked at data from an insurance database of 127,000 German insulin-users and found that diabetics taking low doses of Lantus over a year and a half had a 9% higher chance of developing cancer than people taking traditional human insulin treatments. When patients took higher doses of Lantus, the increased risk of being diagnosed with cancer jumped to 31% over those taking other insulin treatments.

After getting the results from the German data, researchers looked at databases in the U.K., Sweden and Scotland. The Swedish data showed a doubling of the risk of breast cancer, but the U.K. and Scotland studies showed no statistically significant increase connecting Lantus to cancer, prompting Diabetologia’s editors to urge caution at how the results of the studies are interpreted.

Professor Edwin Gale, editor of Diabetologia, and Professor Ulf Smith, president of EASD noted in an editorial accompanying the study that “the characteristics of the groups of patients taking Lantus insulin alone (generally older, higher blood pressure, more overweight) were different to those on other forms of insulin. Thus any difference in cancer risk could be attributed to the pre-treatment characteristics of the groups, rather than the treatment itself. Also, the numbers of cases of breast cancer in the Swedish and Scottish studies were very small, meaning the findings could have occurred due to chance.”

The EASD has said that the studies show an urgent need for more research into Lantus side effects. Smith and Gale say such research should come from more database analysis, as conducting clinical trials would be slow and unethical.

Sanofi officials have called the reports findings inconclusive, standing by the safety of their product. Lantus insulin sales represent about 10% of the company’s pharmaceutical revenue.

Experts stress that patients should not stop using insulin and should contact their doctors to discuss any concerns.