Diabetes Distilled: Increasing cancer mortality in type 2 diabetes: Implications for primary care

Improved diagnosis and management of the cardiovascular complications of diabetes has reduced mortality from these causes, allowing competing causes of mortality to become increasingly important. Indeed, we have previously highlighted in Diabetes Distilled that cancer has now overtaken cardiovascular disease as the leading cause of mortality in people with diabetes (Brown, 2021).

In the present study, published in Diabetologia, the researchers from the Leicester Real World Evidence Unit identified a cohort of 137804 people in England aged ≥35 years newly diagnosed with type 2 diabetes between January 1998 and November 2018 in the Clinical Practice Research Datalink, and assessed trends in all-cause, all-cancer and specific-cancer mortality by gender, age, ethnicity, obesity, socioeconomic and smoking status, and also estimated standardised mortality rates comparing people with type 2 diabetes to the general population. People with diabetes are known to be at increased risk of some types of cancer compared to those without diabetes, and this study sought to identify whether these risks have changed over the last two decades.

Over a median 8.4 years of follow-up, all-cause mortality rates decreased for all ages. However, while cancer mortality rates decreased slightly for 55- and 65-year-olds (1.4% and 0.2% reductions annually, respectively), rates increased annually amongst people aged 75 and 85 years, by 1.2% and 1.6%, respectively. The average annual percentage changes (AAPC) were higher in women than men (1.5% vs 0.5%), although women had lower cancer mortality rates overall than men throughout the years studied. People with morbid obesity had an AAPC of cancer mortality of 5.8% compared with rates of <1% in all other weight groups.

Some findings were less easy to explain, such as the least deprived/wealthiest cohorts having a higher AAPC of 1.5% compared to 1.0% for the most deprived/poorest cohort, resulting in a narrowing but persistent inequality gap. There was a higher AAPC in white subjects (2.4%) compared to a decrease in AAPC in non-white populations. Breast cancer mortality decreased during this period amongst younger women in general, but a 4.1% average annual increase in mortality was identified in younger women with breast cancer and type 2 diabetes.

Implications for practice

While we should continue to focus on reducing cardiovascular mortality in those with type 2 diabetes, the study authors encourage us to be aware of this increasing cancer mortality burden, particularly from colorectal, pancreatic, liver and endometrial cancers, and to take steps to reduce avoidable deaths by encouraging attendance at screening and focusing on earlier diagnosis and management.

Non-alcoholic fatty liver disease is increasing and, in those with type 2 diabetes, is more likely to progress to fibrosis and contributes significantly to the increasing risk of liver cancer – lifestyle and drug interventions may reduce this risk even though drugs are not yet licensed for this indication.

Redoubling our efforts to encourage smokers to quit, and raising their awareness of potentially serious signs and symptoms to facilitate earlier cancer diagnosis, are important in the population at large and, particularly, in those with type 2 diabetes.