Findings from a recent study published in ‘JAMA Oncology’ suggests associations between daily insulin dose and cancer risk in patients with type 1 diabetes. The investigators used patient data from the DCCT and EDIC trial. Evaluation of the risk factors for cancer incidence was done by Cox proportional hazards regression models adjusted for age and sex.

Of the 1303 patients included in the study, 7% had cancer diagnoses during a total of 33,813 person-years of follow-up, which corresponds to an incidence rate of 2.8 (95% CI, 2.2-3.3) per 1000 person-years. The mean age at first diagnosis was 50 years and the mean duration of diabetes at the time was 25 years. The most commonly reported forms of cancer were skin, breast, reproductive, and digestive cancers. Among the 93 patients with cancer diagnoses, 61% were females. Among the cohort, 9% developed cancer within 10 years, 33% developed cancer between 11-20 years, and 58% developed cancer between 21-28 years.

Study results indicated that both age (HR, 1.08 [95% CI, 1.05-1.12]) and female sex (HR, 1.74 [95% CI, 1.15-2.64]) were associated with an increased incidence of cancer. Inverse associations with risk of cancer were observed for exercising habits and high-density lipoprotein cholesterol. However, an association was observed between daily insulin dose and increased incidence of cancer, even after adjustment for age and sex. A limitation of this study is the relatively small sample size, which precluded analyses with specific cancer types and resulted in a wide confidence interval for daily insulin dose.