Co-occurrence of cancer and diabetes in a high-income country: Age-period-cohort projections 2020-2044.

Background: Cancer and diabetes are increasingly prevalent, and it is not unusual for an individual to have both conditions at the same time. This occurrence has significant ramifications to the person, the clinical team providing care, and the broader health system.

Research design and methods: For the period 2006-2019, we used national-level diabetes (Virtual Diabetes Register) and cancer (New Zealand Cancer Registry) data on nearly five million individuals over 44 million person-years of follow-up. We used cancer incidence among those with and without prevalent diabetes to project cancer incidence across the 2020-2044 period, using age-period-cohort modelling to account for factors driving trends in cancer incidence.

Results: Cancer rates were highest among those with diabetes for 21 of the 24 most common cancers, and people with diabetes also have faster projected increases in cancer than those without diabetes. The greatest differences in cancer incidence by diabetes status were for uterine, liver, pancreatic and kidney cancers, which all have a strong relationship with obesity. In terms of projected burden, cancers in people with diabetes were projected to more than double from 20,243 to 48,773, a 141 % increase from 2015 to 19-2040-44. Age-standardised cancer incidence was projected to increase 2.4 times faster for people with diabetes.

Conclusions: Our findings reinforce the fact that diabetes prevention activities are also cancer prevention activities, and must therefore be prioritised and resourced in tandem. The projected volume of diabetes and cancer co-occurrence also has important policy implications in terms of workforce development, as well as service delivery.