Abstract
Background: Despite well-documented inequities in colorectal cancer outcomes between Māori and non-Māori in Aotearoa New Zealand, the underlying contributors to these disparities remain incompletely understood. In particular, there is limited data on the characteristics of colorectal polyps in Māori to inform the conduct of the National Bowel Screening Programme.
Methods: A retrospective cohort study was performed including adult Māori patients who underwent colonoscopy at Waikato Hospital between 2022 and 2024, with an age-matched sample of non-Māori patients. Comparisons were made between groups for disease burden, histological subtypes, and distribution of colorectal polyps and cancer.
Results: A total of 2005 patients were included (n = 1002 Māori, n = 1003 non-Māori). Overall, there were no differences in adenoma detection or polyp characteristics. In the age 50-59 group, Māori had a higher incidence of screening as the indication for colonoscopy (41.5% vs. 3.7%, p < 0.001), as a pilot programme with a screening age reduction for Māori was active during the study. In this group, Māori had higher adenoma detection (48.2% vs. 36.4%, p = 0.006), higher incidence of tubulovillous adenomas (21.5% vs. 13.1%, p = 0.05), and larger polyp size (median 6 mm vs. 5 mm, p < 0.001). For patients ≥ 60 years, cancer stage at diagnosis was higher in Māori (stage 3-4: 37% vs. 24.1%, p = 0.03).
Conclusions: There were no differences overall in the characteristics of colorectal polyps and cancer, suggesting that disparities in outcomes are due to other factors. The discontinued pilot programme with a screening age reduction for Māori demonstrated an opportunity for earlier detection and treatment of precursor lesions to colorectal cancer. Cancer stage was higher in Māori aged ≥ 60 years, for which screening starting at age 50 years would provide an opportunity for earlier disease detection.