The impact of type 2 diabetes on survival in patients with cancer independent of its effect on survival in individuals without cancer: a matched cohort analysis


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Andrew Renehan1,Nasra Alam1,Alison Weight1,Martin Rutter1,Matthew Sperrin1,Darren Ashcroft1,Andrew Renehan1
1University of Manchester, Manchester, UK

Abstract

Background

Patients with cancer and type 2 diabetes (T2D) have a poorer survival than those without T2D. However, studies fail to account for the adverse prognostic effect of T2D on mortality in individuals without cancer. This study aimed to determine whether individuals with cancer and T2D have reduced survival over and above what would be expected by cancer and T2D acting separately i.e. a cancer-T2D interaction.

Method

A matched cohort study was performed in the Clinical Practice Research Datalink (England), linked with national cancer statistics (1998-2015), to derive cohorts with incident versus never cancer, aged 30 to 85 years. We then derived four groups: cancer never T2D (148,467); cancer prevalent T2D (14,124); never cancer never T2D (688,730); never cancer prevalent T2D (57,577). The primary outcome was 10-year overall survival (OS). Results from Cox models with cancer-T2D interactions were expressed as hazard ratios (HRs) and 95% confidence intervals (CIs).

Results

In men, the 10-year OS were: cancer never T2D, 32%; cancer prevalent T2D, 28%; never cancer never T2D 68%; never cancer prevalent T2D, 57%. In women, the respective 10-year OS were: 45%, 36%, 78%, 62%.

In the interaction model for men, the HR (prevalent T2D versus never T2D) was 1.16 (95% CI: 1.13-1.19); interaction term: 0.99 (95% CI: 0.95-1.04). For women, the HR (prevalent T2D versus never T2D) was 1.29 (95% CI: 1.24-1.33); interaction term: 0.78 (95% CI: 0.74-0.82, p < 0.001).

Conclusion

Patients with cancer and T2D had a poorer survival compared with those without T2D. For men, the adverse effect of T2D reflected the adverse prognostic impact of T2D in the non-cancer population; for women, there was evidence that the adverse impact of T2D was lessened among patients with cancer. Understanding these observations through further research will help inform strategies to reduce mortality in patients with cancer and T2D.