The European Association for the Study of Diabetes ( EASD ) made an urgent call for more research into a possible link between use of Insulin Glargine ( an insulin analogue, brand name Lantus ) and increased risk of cancer, following evidence from studies in Germany, Sweden and Scotland. However, until this further research becomes available, these experts are stressing that patients with diabetes taking Lantus should continue to do so, although some might wish to consider alternative types of insulin. The studies are reported in Diabetologia, the journal of EASD.

Worldwide, there are over 200 million people with diabetes. About 10% of these develop diabetes in early life, and most of them have what is known as type 1 diabetes. People with type 1 diabetes have an absolute reliance upon insulin treatment for their continued health and well-being. Type 2 diabetes, which affects the remaining 90%, typically develops later in life and may be associated with excess weight. People with type 2 diabetes are able to make some of their own insulin, which means that they can usually be treated with diet and tablets in its early stages. At a later stage, however, many patients with type 2 diabetes lose the ability to produce their own insulin, and will then need insulin injections to maintain their health.

Human insulin has been widely used for decades and its safety is beyond doubt; this new information relates to an artificial form of Insulin, or Insulin analogue, called Insulin Glargine which has been widely used since 2000.
The concerns about a possible link between use of Lantus Insulin and increased cancer risk were raised by a German study of around 127,000 insulin-treated patients in an insurance database. The research identified a statistically significant link between patients who had used Lantus Insulin and those who had been diagnosed with cancer. Compared with people using similar doses of human Insulin, out of every 100 people who used Lantus Insulin over an average of about one-and-a-half years, one additional person was diagnosed with cancer. Of particular note in this study was the finding that the increased risk of cancer was dose-dependent. Thus for patients given a dose of 10 U, Lantus Insulin alone increased the risk of cancer by 9% compared with human Insulin; but for a dose of 50 U, the increased risk was 31%. The study did not consider Insulin Detemir ( Levemir ), an Insulin analogue whose action is prolonged by a different principle from Lantus.

To confirm these results, other studies have been performed using databases from Sweden, Scotland, and the UK. The Swedish study found that compared with patients on insulins other than Lantus Insulin, patients on Lantus Insulin alone had double the risk of breast cancer. The Scottish study found a non-significant increased risk for breast cancer specifically. The UK study found no link between Insulin Glargine and cancer.

However, the studies have limitations. The main one is that, although the data were adjusted for a number of variables, 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. They state categorically that Lantus and other insulins do not cause cancer, but these studies expose the possibility that Lantus Insulin could cause existing cancer cells to grow and divide more rapidly, which might explain why more cancers came to be diagnosed over 1-3 years of observation.

Source: EASD, 2009

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