Insulin use tied to cancer risk in study
PARIS — Diabetics who take insulin have a higher risk of developing cancer, according to Danish researchers who say they cannot explain the link.
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 association’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, 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.
“People who are on insulin have a higher risk of developing cancer,’’ Carstensen said in a telephone interview yesterday. “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 who did not have diabetes, according to the abstract. They observed 30,000 cancer cases among diabetics, including tumors of the digestive tract, liver, and pancreas.
Diabetes causes blood-sugar levels to be higher than normal. Insulin, a hormone made in the pancreas, helps convert blood sugar into energy. Diabetics either do not produce enough insulin naturally, or their bodies have trouble using it properly. Glucose-lowering therapies such as Sanofi-Aventis’s Lantus, the first once-a-day form of insulin, have become standard care for people who can’t control their blood sugar levels with healthy eating or exercise.
This isn’t the first time researchers have sought to shed light on the link between insulin use and higher cancer risk.
Last year, Ralph DeFronzo, a researcher at the University of Texas Health Science Center, said on a conference call that studies would show Lantus was tied to cancer. Shares in Paris-based Sanofi slumped after that call. The research, published in the journal Diabetologia, delivered mixed results, and the Food and Drug Administration said it didn’t prove a link.
Another study, based on 1,500 patients and published in June in the journal Diabetes Care, also tied insulin glargine, the chemical name for Lantus, to a higher tumor risk.
France’s biggest drugmaker remains confident on the safety of Lantus, Sanofi Chief Medical Officer Jean-Pierre Lehner said.