Capturing diversity in cancer incidence and outcomes among the New Zealand Pacific population using linked administrative data.

Aim: The New Zealand population defined as "Pacific" is ethnically diverse, but this diversity is seldom examined in health research. This paper applies novel methods for describing health outcomes for specific Pacific populations in New Zealand using all-cancer and gastric cancer incidence and mortality as examples. Effects of loss to follow-up from leaving the country are also assessed.

Method: The New Zealand Cancer Registry was linked to administrative datasets and analysed within Stats NZ's Integrated Data Infrastructure (IDI). All-cancer and gastric cancer incidence was examined over the 1995-2022 period, as well as 1-5-year mortality among 1998-2017 diagnoses.

Results: There was variability in age-standardised all-cancer incidence and gastric cancer incidence for different Pacific groups. Less variation in mortality was identified between groups, and these rates increased only modestly when adjusting for those who left the country. Lower all-cancer mortality was observed in 2008-2017 compared with 1998-2007.

Conclusion: Variation in health outcomes among specific Pacific ethnicities is masked when examining Pacific peoples as an aggregated ethnic group. However, small counts among small ethnicities create challenges for producing detailed, reliable data when using the IDI.