New research shows that cancer mortality in people with type 2 diabetes is substantially higher than the general population, by 18% for all cancers combined, 9% for breast cancer and 2.4 times for colorectal cancer.
Cancer mortality in people with diabetes was around double that in the general population for diabetes-related cancers including liver, pancreatic and endometrial (women only) cancers, said the paper published in Diabetologia, the journal of the European Association for the Study of Diabetes.
The study, by Dr Suping Ling, Leicester Real World Evidence Unit, Leicester Diabetes Research Centre, University of Leicester, and London School of Hygiene and Tropical Medicine, UK, also showed increasing breast cancer mortality rates by 4.1% per year, in the younger women with type 2 diabetes, across the 20-year study period from 1998-2018.
Accumulating epidemiological evidence has shown a higher risk of incidence and mortality for some types of cancer in individuals with type 2 diabetes, with prolonged exposure to the effects of increased blood sugar and insulin levels, insulin resistance and chronic inflammation being the potential underlying biological mechanisms.
The evidence indicates that there is a causal relationship between type 2 diabetes and pancreatic, liver and endometrial cancer. While previous studies have extensively investigated inequalities in cardiovascular outcomes among people with type 2 diabetes, less is known about whether such inequalities exist in cancer mortality rates.
In this study, the authors used a cohort of individuals aged 35 years or over who had newly diagnosed type 2 diabetes in the Clinical Practice Research Datalink, a UK general practice database, over a 20-year period between 1 January 1998 and 30 November 2018.
Then, they analysed trends in all-cause, all-cancer and cancer-specific mortality rates by age, gender, ethnicity, socioeconomic status, obesity and smoking status. They also estimated standardised mortality ratios comparing mortality rates in people with type 2 diabetes with the general population.
The study included 137,804 individuals with newly diagnosed type 2 diabetes with median follow-up of 8.4 years. The authors found all-cause mortality rates decreased at all ages between 1998 and 2018; cancer (all cancers combined except non-melanoma skin cancer) mortality rates also decreased for 55-year-olds (by 1.4% per year) and 65-year-olds (by 0.2% per year) but increased for 75-year-olds (by 1.2% per year) and 85-year-olds (by 1.6% per year).
The authors say diabetes screening, better management of diabetes and its complications, earlier cancer detection and improved cancer treatments seem to have benefited younger people with T2D in the same way as they have in the general population.
Smokers vs non-smokers
The gap in cancer mortality between smokers and non-smokers also increased, with smokers seeing an increased cancer mortality AAPC of 3.4%, while for non-smokers the AAPC fell by 1.4%.
The authors suggest current healthcare policies and structures could benefit never-smokers more than smokers – and that tailored interventions for smokers such as specific screening programs could help address increasing cancer mortality among them, said the study.
The authors said their findings underline the growing cancer burden in people with type 2 diabetes, particularly in older individuals, and highlight the need to prioritise cancer prevention, research and early detection and management in this population, especially for colorectal, pancreatic, liver and endometrial cancer, whose mortality rates were substantially higher in individuals with type 2 diabetes.