Investigating the Association Between Individual Income and Cancer Outcomes Among Canadians Diagnosed with Gastric Cancer
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Authors
Howden, Robert Alexander McKenley
Date
2025-08-07
Type
thesis
Language
eng
Keyword
gastric cancer , socioeconomic status , income , social determinants of health , oncology , cancer , epidemiology , public health
Alternative Title
Abstract
Background: A growing body of research continues to document income-based disparities in cancer outcomes. The first objective of this study was to investigate the association between individual income and diagnosis with stage IV gastric cancer, and the second objective of this study was to investigate the association between individual income and death from any cause in the five years following diagnosis.
Methods: In Canadians diagnosed with gastric cancer between 2010 and 2019, this thesis used the Statistics Canada Canadian Census Health and Environmental Cohorts to investigate the association between individual income and diagnosis with stage IV gastric cancer using logistic regression, and the association between individual income and death from any cause within five years using Cox proportional hazards regression. Effect modification was tested, and sensitivity analyses were performed.
Results: 8,545 Canadians were diagnosed with gastric cancer during the study period and met the study inclusion criteria; 1,900 were diagnosed in provinces where greater than 75% of people had TNM stage data recorded in the Canadian Cancer Registry. In the cohort of 1,900 people, we observed no association between individual income quintile and presentation with stage IV diagnosis (p=0.32) and no difference in presentation with stage IV disease at diagnosis between patients in the lowest and highest income quintiles (OR: 0.87, 95% CI: 0.64-1.19). In the cohort of 8,545 people, we observed a significant association between individual income quintile and death from any cause in the five years following diagnosis (p=0.003), with patients within the lowest income quintile having 1.18 times the risk of death when compared to patients within the highest income quintile (HR: 1.18, 95%.CI: 1.08-1.29). No effect modification was detected, and sensitivity analyses were consistent with the primary analyses.
Conclusion: While we observed no income-based difference in the odds of presenting with stage IV gastric cancer diagnosis, a higher proportion of Canadian gastric cancer patients with low incomes die from any cause in the five years following diagnosis relative to those with high incomes. Future research should investigate the mechanisms underlying the association observed in this study and the effect of immigration on Canadian gastric cancer outcomes.