Because up to 10% of adults have diabetes and because a substantial proportion will ultimately be prescribed insulin, reports that insulin therapies may be associated with cancer are of significant concern.1-2 This Commentary highlights limitations of the literature and notes that the evidence is also consistent with the hypothesis that insulin therapy targeting good glycemic control might actually reduce cancers.

Is an Elevated Glucose Level a Risk Factor for Cancers?

Type 2 diabetes is an independent risk factor for several cancers,3 and this relationship parallels the relationship between obesity and cancer. For type 1 diabetes, prospective studies report a modest 20% increased risk of stomach, endometrial, and cervical cancer and a 2-fold higher risk of pancreatic cancer. Prospective studies also suggest that glucose levels above normal predict cancers. For example, in a 10-year follow-up of more than 1 million Korean adults, there was a progressive relationship among fasting glucose levels above normal, cancers, and cancer .