Insulin glargine and risk of cancer: a cohort study in the French National Healthcare Insurance Database

Using the Echantillon G,n,raliste de B,n,ficiaires: random 1/97 permanent sample of the French national healthcare insurance system database (EGB), we investigated whether, as previously suspected, the risk of cancer in insulin glargine (A21Gly,B31Arg,B32Arg human insulin) users is higher than in human insulin users. The investigation period was from 1 January 2003 to 30 June 2010. We used Cox proportional hazards time-dependent models that were stratified on propensity score quartiles for use of insulin glargine vs human insulin, and adjusted for insulin, biguanide and sulfonylurea possession rates to assess the risk of cancer or death in all or incident exclusive or predominant (>= 80% use time) users of insulin glargine compared with equivalent human insulin users. Only type 2 diabetic patients were studied. Exposure rates varied from 2,273 and 614 patient-years for incident exclusive users of insulin glargine or human insulin, respectively, to 3125 and 2341 patient-years for all patients predominantly using insulin glargine or human insulin, respectively. All-type cancer HRs with insulin glargine vs human insulin ranged from 0.59 (95% CI 0.28, 1.25) in incident exclusive users to 0.58 (95% CI 0.34, 1.01) in all predominant users. Cancer risk increased with exposure to insulin or sulfonylureas in these patients. Adjusted HRs for death or cancer associated with insulin glargine compared with human insulin ranged from 0.58 (95% CI 0.32, 1.06) to 0.56 (95% CI 0.36, 0.87). There was no excess risk of cancer in type 2 diabetic patients on insulin glargine alone compared with those on human insulin alone. The overall risk of death or cancer in patients on insulin glargine was about half that of patients on human insulin, thereby excluding a competitive risk bias.