According to a study, diabetic's risk of cancer increases if they use the long-acting insulin analogue glargine instead of human insulin.
Led by a collaborative team of researchers from the Institute for Quality and Efficiency in Health Care (IQWiG) and a research institute of the German Local Health Care Fund, the study analysed the data of almost 130,000 patients with diabetes in Germany who had been treated with either human insulin or the insulin analogues lispro (trade name: Humalog), aspart (Novorapid) or glargine (Lantus) between January 2001 and June 2005.
Writing about their study in the journal Diabetologia, the official organ of the European Association for the Study of Diabetes (EASD), the researchers say that the disturbing result is that malignancies were found more frequently in patients treated with glargine than in those prescribed a comparable dose of human insulin.
"Our analysis does not provide absolute proof that glargine promotes cancer. Our study does, however, arouse an urgent suspicion which should have consequences for the treatment of patients," says Peter T. Sawicki, IQWiG's Director and co-author of the study.
The researchers have revealed that no difference was found between the short-acting insulin analogues, lispro and aspart, and human insulin.
Insulin analogues are synthetic molecules that do not occur naturally, whereas human insulin matches the insulin that the human body manufactures itself.
The study also revealed that the risk of cancer rose further with increasing glargine dose when compared to human insulin.
The researchers say that the dose-dependent relationship with glargine also confirms the suspicion that the drug plays a causal role.
However, add the research team, the latest study is no reason for patients with diabetes to change their treatment hastily, especially if the glargine dose used is low.
Diabetes is a complex disease and many aspects need to be considered in its treatment.
"However, if a patient can be treated equally well with human insulin as with glargine, then, after consultation with his or her doctor, the patient should consider changing to human insulin. If at all possible, patients with an increased risk of cancer should use human insulin instead of glargine," says Sawicki.
The researchers have no evidence that glargine or other insulin agents transform normal cells to cancer cells.
However, it may be possible that glargine stimulates the growth of existing cancer cells more strongly than other types of insulin, they add.