Abstract
Māori, the indigenous people of New Zealand, experience disproportionate rates of stomach cancer, compared to non-Māori. The overall aim of the study was to better understand the reasons for the considerable excess of stomach cancer in Māori and to identify priorities for prevention. Māori stomach cancer cases from the New Zealand Cancer Registry between 1 February 2009 and 31 October 2013 and Māori controls, randomly selected from the New Zealand electoral roll were matched by 5-year age bands to cases. Logistic regression was used to estimate odd ratios (OR) and 95% confidence intervals (CI) between exposures and stomach cancer risk. Post-stratification weighting of controls was used to account for differential non-response by deprivation category. The study comprised 165 cases and 480 controls. Nearly half (47.9%) of cases were of the diffuse subtype. There were differences in the distribution of risk factors between cases and controls. Of interest were the strong relationships seen with increased stomach risk and having >2 people sharing a bedroom in childhood (OR 3.30, 95%CI 1.95–5.59), testing for H pylori (OR 12.17, 95%CI 6.15–24.08), being an ex-smoker (OR 2.26, 95%CI 1.44–3.54) and exposure to environmental tobacco smoke in adulthood (OR 3.29, 95%CI 1.94–5.59). Some results were attenuated following post-stratification weighting. This is the first national study of stomach cancer in any indigenous population and the first Māori-only population-based study of stomach cancer undertaken in New Zealand. We emphasize caution in interpreting the findings given the possibility of selection bias. Population-level strategies to reduce the incidence of stomach cancer in Māori include expanding measures to screen and treat those infected with H pylori and a continued policy focus on reducing tobacco consumption and uptake.
Highlights
Stomach cancer has declined in incidence over the past 4–5 decades, it remains an important public health problem and is still one of the most common cancers worldwide [1]
A total of 296 Māori with stomach cancer were identified from histological reports sent to the NZ Cancer Registry (NZCR) for the 5 year time period of the study
There were no differences in median age (58 years) or gender between eligible case participants and non-participants; there were differences by NZDep2006 categories, for Q3 (13% vs 5% respectively)
Summary
Stomach cancer has declined in incidence over the past 4–5 decades, it remains an important public health problem and is still one of the most common cancers worldwide [1]. 95% of stomach cancers are adenocarcinomas, divided histologically into two major subtypes: intestinal and diffuse [6]. Declines in stomach cancer incidence over the past forty years have occurred primarily for the intestinal type [7]. Māori appear to develop stomach cancer at a younger age and have a higher incidence of diffuse adenocarcinomas compared to non-Māori [8,9]. Diffuse tumours are seen in hereditary diffuse gastric cancer which is associated with germline E-cadherin gene (CDH1) alterations [10] reasons for the higher incidence of sporadic diffuse cancers in Māori remain unclear
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