Gastric Cancer in Northern Canadian Populations: A Focus on Cardia and Non-Cardia Subsites

Abstract

In northern Canada where there is a high prevalence of Helicobacter pylori infection, there is a paucity of information on gastric cancer by the topographical subsites cardia (CGC) and non-cardia (NCGC). Here we describe the incidence of CGC and NCGC, separately, among northern Canadian populations. We used data from the Cancer Incidence in Five Continents Volumes X (CI5X) and XI (CI5XI) to obtain CGC and NCGC incidence for Canada and for Yukon (YT), a northern Canadian territory. Using these data with those provided by the Government of the Northwest Territories (NT), we estimated standardized incidence ratios comparing northern populations to Canada as a whole. We also estimated age-standardized incidence rates to permit comparisons across populations globally. NT and YT populations were disproportionately impacted by gastric cancer, particularly NCGC. This was especially true for Indigenous populations: NCGC incidence rates among NT Indigenous men were 2.7 times the rates among all men in Canada, while rates among NT Indigenous women were 3.1 times the rates among all women in Canada. Similarly, age-standardized rates of NCGC among Indigenous NT residents were comparable to global regions where there is a high burden of NCGC. This study has, for the first time, quantified the incidence of CGC and NCGC for the NT and YT, providing new insights into the burden of these cancers among northern Canadian populations.

Keywords: Arctic; Canada; Helicobacter pylori; Indigenous health; cardia; epidemiology; gastric cancer; incidence.

Figure 1

Age distribution of total gastric cancer cases by population; northern territories, Canada; various years. Canada and Yukon include cases diagnosed 2003–2012; Northwest Territories (NT) includes cases diagnosed 1997–2015.

Figure 2

Proportional NCGC incidence (NCGC cases divided by total gastric cancer cases); northern territories, Canada; various years. Canada and Yukon include cases diagnosed 2003–2012; Northwest Territories (NT) includes cases diagnosed 1997–2015. Non-cardia gastric (NCGC) defined as C16.1-9. 95% confidence intervals are based on the binomial exact distribution.

Figure 3

(a) Estimated cardia gastric cancer age-standardized incidence rates (ASRs per 100,000) by population and sex; (b) Estimated non-cardia gastric cancer ASRs (per 100,000) by population and sex; northern territories, Canada, and world regions, various years. Age-standardized incidence rates (ASRs) standardized to the World Population. Canada and Yukon include cases diagnosed during 2003–2007; Northwest Territories (NT) includes cases diagnosed during 1997–2015. World and regional cardia and non-cardia gastric cancer ASR estimates from Colquhoun, et al. (2014) [2].

Figure 3

(a) Estimated cardia gastric cancer age-standardized incidence rates (ASRs per 100,000) by population and sex; (b) Estimated non-cardia gastric cancer ASRs (per 100,000) by population and sex; northern territories, Canada, and world regions, various years. Age-standardized incidence rates (ASRs) standardized to the World Population. Canada and Yukon include cases diagnosed during 2003–2007; Northwest Territories (NT) includes cases diagnosed during 1997–2015. World and regional cardia and non-cardia gastric cancer ASR estimates from Colquhoun, et al. (2014) [2].