The Incidence of Cancer Overall and Site-Specific Cancer Among Patients with Type 2 Diabetes Between 1988 and 2019

Date of ISAC Approval: 
08/07/2020
Lay Summary: 
Type 2 diabetes mellitus is a commonly diagnosed chronic disease resulting in considerable morbidity and mortality. An important cause of increased morbidity in diabetes is higher occurrence of cancer among patients with diabetes. However, whether the occurrence of cancer in diabetes has changed over time is unclear. This is concerning because the occurrence of cancer has increased over the last several decades, with substantial costs to the health system, particularly when diagnosed at late stages. The current study will use the United Kingdom Clinical Practice Research Datalink to investigate whether the occurrence of cancer among patients with type 2 diabetes compared with non-diabetic individuals has changed over time. Knowledge derived from this study might enable health authorities to screen for cancer among patients with diabetes, in the process diagnosing such cancer early and managing it more effectively.
Technical Summary: 
Epidemiological studies have established the association between diabetes and the risk of cancer. Various factors that might influence the incidence of cancer in diabetes have altered over time. They include the introduction of novel antidiabetic drugs and longer survival of patients with diabetes. Whether the incidence of cancer in patients with diabetes has varied over time is unclear. This study will use the Clinical Practice Research Datalink to assemble patients at least 40 years of age newly-treated for type 2 diabetes between 1988 and 2018. These patients with type 2 diabetes will be matched with non-diabetic individuals using risk set sampling. Poisson regression models conditional on matched pairs will be used to estimate incidence rate ratios with 95% confidence intervals comparing the incidence rates of cancer overall and site-specific cancer, separately, between patients with type 2 diabetes and individuals from the non-diabetic population for each year between 1988 and 2018. Secondary analyses will stratify the incidence by age and sex and examine the effect of duration of diabetes.
Health Outcomes to be Measured: 
Cancer overall and site-specific cancer (cancer of the breast, prostate, lung, colon and rectal, kidney, head and neck, central nervous system, pancreas, bladder, endometrium, oesophagus, ovary, stomach, liver and biliary tract, and thyroid, melanoma and non-melanoma skin cancer, non-Hodgkin lymphoma, leukaemia, and myeloma).
Collaborators: 

Dr Samy Suissa - Chief Investigator - McGill University
Dr Laurent Azoulay - Corresponding Applicant - McGill University
Oriana Hoi Yun Yu - Collaborator - Sir Mortimer B Davis Jewish General Hospital
Dr Richeek Pradhan - Collaborator - Sir Mortimer B Davis Jewish General Hospital
Dr Robert Platt - Collaborator - McGill University