Insulin Users Have 50% Higher Cancer Risk; Causes Unclear

Patients on insulin were 50 percent more likely to get cancer compared with the general population, researchers led by Bendix Carstensen from the Steno Diabetes Center in Gentofte, Denmark, wrote in an abstract of the study posted on the website of the European Association for the Study of Diabetes. The findings will be presented next month in Stockholm at the EASD's annual conference.  

People with diabetes already have a higher risk of cancer, the researchers said, and the tumor development seen in this study may not be caused by insulin itself, according to Carstensen, senior statistician at the center. It may be the result of contributing causes common to cancer, diabetes and insulin use, such as obesity, he wrote in the abstract. The study, conducted on the Danish population, is the largest of diabetes and cancer incidence so far, Carstensen said.

Carstensen stated that, "People who are on insulin have a higher risk of developing cancer… But what the reason for that is, it's not clear from this study nor from any other study."

In order to follow diabetes patients and see how many of them developed cancer, researchers created links between the Danish National Diabetes Register and the Danish Cancer Register. They compared their findings with data on tumor occurrence among people not suffering from diabetes, according to the abstract. They observed a total of 30,000 cancer cases among diabetics, including tumors of the digestive tract, liver and pancreas.

This is not the first time that researchers have sought to shed light on the possible link between insulin use and higher cancer risk.

Last year, Ralph DeFronzo, a researcher at the University of Texas Health Science Center, said that studies would show Lantus was tied to cancer. The research, published in Diabetologia, delivered mixed results, and the FDA said it didn't prove a link.

Another study, based on 1,500 patients and published in June in Diabetes Care, also tied insulin glargine, the chemical name for Lantus, to a higher tumor risk.

The Danish study will be presented on Sept. 23 in Stockholm, according to the EASD's website.