Does Insulin Glargine Increase the Risk of Cancer Compared With Other Basal Insulins?

OBJECTIVE To explore in France the relationship between insulin glargine use and overall and specific cancer risks in type 2 diabetic patients compared with other basal insulins. RESEARCH DESIGN AND METHODS Data were extracted from French health insurance information system (Système National d'Information Inter-Régimes de l'Assurance Maladie) linked with data from the French Hospital Discharge database (Programme de Médicalisation des Systèmes d'Information). Included were 70,027 patients aged 40-79 years who started a basal insulin in 2007-2009. Cox proportional hazards models with age as time-scale were used to calculate multivariate-adjusted hazard ratios for associations between type of basal insulin and risk of overall cancer, breast cancer, and seven other cancer sites. RESULTS The median follow-up was 2.67 years in patients exposed to insulin glargine. Absolute event rates for all cancer in patients exposed to glargine versus other basal insulin users were 1,622 and 1,643 per 100,000 person-years, respectively. No significant association was observed between glargine exposure and overall cancer incidence after adjustment for sex, with a hazard ratio of 0.97 (95% CI 0.87-1.07), or after additional adjustment for any other hypoglycemic agent use and duration of diabetes. No increased risk of breast cancer was observed for glargine users compared with other basal insulins users, with a fully adjusted hazard ratio of 1.08 (0.72-1.62). CONCLUSIONS In a large cohort of patients newly treated by basal insulin, no increased risk of any cancer was observed in insulin glargine users compared with other basal insulin users. Because follow-up did not exceed 4 years, longer-term studies are needed.