The impact of immigration status on cancer outcomes in Ontario, Canada.

Abstract

285 Background: In the delivery of cancer care, barriers to access could potentially result in inferior outcomes and survival. Although a relationship has been demonstrated between disadvantaged socio-economic status and mortality, the impact of immigration on outcomes is less clear. Methods: Administrative databases were linked to create a cohort of all incident cases of colorectal, lung, prostate, head/neck, breast and hematologic malignancies from Jan 2000 to Dec 2012 in Ontario, Canada. Cases were defined according to immigration status and followed from diagnosis until death (or cancer-specific death). Cox proportional hazards models were constructed to study the impact of immigration status on survival after adjusting for relevant variables. Additional adjusted models studied the relationship of time since immigration on mortality. Results: During the study period, 11,485 cancer cases were diagnosed in recent immigrants (0-10 years in Canada), 17,844 cases in non-recent immigrants (11-25 years), and 416,118 cases in non-immigrants. Following adjustment for relevant predictors by Cox regression, survival was improved for recent immigrants (HR 0.843; 95% CI 0.814-0.873) and non-recent immigrants (HR 0.902; 95% CI 0.876-0.928) compared to non-immigrants. Cancer-specific survival was also better for recent immigrants (HR 0.857; 95% CI 0.823-0.893) and non-recent immigrants (HR 0.907; 95% CI 0.875-0.94) compared to non-immigrants. Amongst immigrants, each year from the original landing in Canada was associated with increased mortality (HR 1.004; 1.000-1.009) and a trend to increased cancer-specific mortality (HR 1.005; 0.999-1.010) that was not statistically significant. Immigrants from all WHO world regions were found to have similar reductions in mortality and cancer-specific mortality. Conclusions: Immigrants to Canada demonstrate a “healthy immigrant” effect, with lower mortality compared to Canadian-born individuals. This benefit appears to diminish over time, as the health of immigrants potentially converges with the Canadian norm. Potential contributors to the benefit include self-selection for immigration, health requirements for entrance, and differences in disease distribution related to ethnicity.