Abstract
Cancer is a leading cause of death globally and in New Zealand (NZ), and its prevalence will rise as our population ages. Recent projections indicate that there will be an approximate doubling of cancer patients aged over 65 in the Oceania region by 2035. Aside from the incalculable human cost associated with a substantial rise in the number of new cancer patients, such a rise will also exert extra pressure on public cancer services (from diagnosis through to treatment), which are already pressed to meet current demand.
Rates of diabetes mellitus (hereafter diabetes) are increasing in NZ by a staggering 7% per year, and are around three times higher among Mãori and Pacific people than in Europeans. At the heart of this epidemic is Type 2 diabetes - a form of the disease caused by factors including obesity and poor access to physical activity, and characterised by disruptions to the normal processes for regulation of glucose in the bloodstream. In 2018, around 253,000 New Zealanders had some form of diabetes,6 with 90-95% of these likely to be Type 2.
It is not unusual for an individual to have both cancer and diabetes, given they are individually common. Based on international evidence, we might expect around 35% of the population to be diagnosed with diabetes and 44% with cancer in their lifetime; with around 15% diagnosed with both. This co-occurrence matters: people with diabetes have poorer survival from cancer (including women with breast cancer), with a large meta-analysis finding that cancer patients with diabetes were 41% more likely to die than cancer patients without diabetes.
But why do diabetes and cancer co-occur? How does diabetes lead to poorer outcomes among those with cancer? Crucially, what are the ramifications of this co-occurrence for Mãori and Pacific peoples, given the inequitable burden of both conditions shouldered by these populations? In this section, we examine the literature and summarise the current evidence, and identify the key questions that remain unanswered.
Note: This report includes some results that are currently under peer review, and as such may not be in their final form at the time of writing (January 2024). The results that are published in peer-reviewed journals should be considered the final form of output from this project.