RESUMO
BACKGROUND: Substantial cancer-related disparities exist between First Nations and non-Indigenous Canadians. The objectives of this study were to compare cancer incidence, stage at diagnosis and mortality outcomes between Status First Nations people living on reserve and off reserve in Manitoba. METHODS: We conducted a retrospective analysis of population-level administrative health databases in Manitoba. Cancers diagnosed between Apr. 1, 2004, and Mar. 31, 2011, were linked with the Indian Registry System and 5 provincial databases. We compared differences in baseline characteristics, cancer incidence, site and stage at diagnosis between Status First Nations patients living on and off reserve. Linear regression models examined trends in annual cancer incidence. Cox proportional hazard regression models examined mortality. RESULTS: There were 1524 newly diagnosed cancers among Status First Nations people in Manitoba between Apr. 1, 2004, and Mar. 31, 2011. First Nations people living on reserve were significantly older than those living off reserve (p < 0.001) and had higher Charlson Comorbidity Index scores at diagnosis (p = 0.01). A lower proportion of on-reserve patients than off-reserve patients were diagnosed with stage I cancers (21.7% v. 26.9%, p = 0.02). There were no differences in annual cancer incidence between groups. The adjusted incidence of cancer over the combined study years was higher in the off-reserve group than in the on-reserve group (287.9 v. 247.9 per 100 000, p = 0.02). No significant differences in mortality were found. INTERPRETATION: The lower proportion of on-reserve patients diagnosed with cancer at stage I is concerning, as it suggests less access to screening services or delays in diagnosis. Further research is needed to understand patterns in diagnosis and differences in cancer site and overall cancer incidence between First Nations people living on and off reserve.
RESUMO
BACKGROUND: Globally, epidemiological evidence suggests cancer incidence and outcomes among Indigenous peoples are a growing concern. Although historically cancer among First Nations (FN) peoples in Canada was relatively unknown, recent epidemiological evidence reveals a widening of cancer related disparities. However evidence at the population level is limited. The aim of this study was to explore cancer incidence, stage at diagnosis, and outcomes among status FN peoples in comparison with all other Manitobans (AOM). METHODS: All cancers diagnosed between April 1, 2004 and March 31, 2011 were linked with the Indian Registry System and five provincial healthcare databases to compare differences in characteristics, cancer incidence, and stage at diagnosis and mortality of the FN and AOM cohorts. Cox proportional hazard regression models were used to examine mortality. RESULTS: The FN cohort was significantly younger, with higher comorbidities than AOM. A higher proportion of FN people were diagnosed with cancer at stages III (18.7% vs. 15.4%) and IV (22.4% vs. 19.9%). Cancer incidence was significantly lower in the FN cohort, however, there were no significant differences between the two cohorts after adjusting for age, sex, income and area of residence. No significant trends in cancer incidence were identified in either cohort over time. Mortality was generally higher in the FN cohort. CONCLUSIONS: Despite similar cancer incidence, FN peoples in Manitoba experience poorer survival. The underlying causes of these disparities are not yet understood, particularly in relation to the impact of colonization and other determinants of health.