The Use of Long-Acting Insulin Analogs and the Risk of Colorectal Cancer Among Patients with Type 2 Diabetes: A Population-Based Cohort Study

Introduction: The association between long-acting insulin analogs and colorectal cancer is uncertain, with previous studies reporting discrepant findings. 

Objective: To determine whether the use of long-acting insulin analogs is associated with an increased risk of colorectal cancer, when compared with use of intermediate-acting human insulins among patients with type 2 diabetes. 

Methods: We conducted a population-based study using the United Kingdom Clinical Practice Research Datalink (CPRD). We identified patients newly treated with either a long-acting insulin analog or an intermediate-acting human insulin between September 1, 2002 and January 31, 2018, with follow-up until January 31, 2019. Each long-acting insulin analog user was propensity score-matched to one intermediate-acting human insulin user, and a lag of 1 year was imposed. Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) of colorectal cancer, comparing long-acting insulin analogs with intermediate-acting human insulin. Secondary analysis was conducted to assess whether there was a duration–response relationship. Results: A total of 10,734 new long-acting insulin analog users were matched to 10,734 new intermediate-acting human insulin users. After a median follow-up of 2.8 years, the use of long-acting insulin analogs was not associated with an increased risk of colorectal cancer, compared with intermediate-acting human insulin (1.80 vs. 1.87 per 1000 person-years, respectively; HR 0.96, 95% CI 0.70–1.34). There was no evidence of a duration–response relationship. 

Conclusions: The results of this population-based study indicate that use of long-acting insulin analogs is not associated with an overall increased risk of colorectal cancer.