Is the Incidence of Early-Onset Adenocarcinomas in Aotearoa New Zealand Increasing?

Abstract

Aim: The incidence of certain cancers in those under 50 years old (early-onset cancers) has been rising in many countries. This increase is generally unexplained and has significant implications for health policies and treatment. We wish to understand if this trend is occurring in Aotearoa New Zealand and whether it is across the spectrum of adenocarcinomas or site (cancer location)-specific. Differences in patterns between sites would suggest different possible etiologies for any increase in incidence and hence differences in how this trend might be managed. Method: The change in incidence of esophageal, gastric, colorectal, pancreatic, breast, lung, uterine, ovarian, and prostate adenocarcinomas from 2000 to 2020 in Aotearoa New Zealand was analyzed. Data was extracted from the New Zealand Cancer Registry. All new cases of relevant adenocarcinomas were analyzed to calculate the crude incidence, incidence rate ratios (IRRs), and age-standardized incidence. Trends were estimated by age and ethnicity, focusing on early-onset adenocarcinomas. Results: There was evidence for increases in early-onset colorectal (IRR 1.23, p < 0.01), breast (IRR 1.08, p < 0.01), uterine (IRR 1.73, p < 0.01), and prostate adenocarcinomas (IRR 1.14, p < 0.05). In Māori, there was evidence for significant increases in colorectal (IRR 1.42, p < 0.01), uterine (IRR 1.98, p < 0.01), and lung adenocarcinomas (IRR 1.23, p < 0.05). Conclusion: From 2000 to 2020, there were increases in multiple early-onset adenocarcinomas. This is site-specific, namely colorectal, breast, uterine, and prostate. Ongoing research is needed to investigate possible causes and develop strategies to address the increase in site-specific early-onset adenocarcinoma incidence.