Cancer risk in diabetic patients treated with insulin glargine?

Insulin glargine was the first long-acting human insulin analogue to be authorised in the European Union, in the early 2000s, for the treatment of diabetes mellitus. It has about a 6-fold increase in affinity for the insulinlike growth factor 1 (EGF-1) receptor compared with natural human insulin, which may stimulate tumour development. Four European epidemiological studies published in 2009 examined the risk of cancer in diabetic patients treated with insulin glargine. One of these studies, conducted in Germany, showed a statistically significant dose-dependent increase in the risk of cancer. Two other studies, one in Scotland and the other in Sweden, showed an increase in the risk of breast cancer. The fourth study, conducted in the UK, showed a lower risk of cancer in patients on metformin. This evidence is inconclusive, notably because these studies did not take confounding factors into account. Nevertheless, the results tend to be similar and consistent with certain pharmacological mechanisms. In practice, pending more solid evidence, these epidemiological results should be taken into account when weighing the risk-benefit balance of insulin therapy for diabetic patients, on a case by case basis, depending on the type of diabetes, patient history, life expectancy, and the possible practical advantages of insulin glargine.