Impact of immigration status on cancer outcomes in Ontario, Canada

Background — Prior studies have documented inferior health outcomes in vulnerable populations, including racial minorities and those with disadvantaged socioeconomic status. The impact of immigration on cancer-related outcomes is less clear.

Methods — Administrative databases were linked to create a cohort of incident cancer cases (colorectal, lung, prostate, head and neck, breast, and hematologic malignancies) from 2000 to 2012 in Ontario, Canada. Cancer patients who immigrated to Canada (from 1985 onward) were compared with those who were Canadian born (or immigrated before 1985). Patients were followed from diagnosis until death (cancer-specific or all-cause). Cox proportional hazards models were estimated to determine the impact of immigration on mortality after adjusting for explanatory variables. Additional adjusted models studied the relationship of time since immigration and cancer-specific and overall mortality.

Results — From 2000 to 2012, 11,485 cancer cases were diagnosed in recent immigrants (0 to 10 years in Canada), 17,844 cases in nonrecent immigrants (11 to 25 years), and 416,118 cases in nonimmigrants. After adjustment, the hazard of mortality was lower for recent immigrants (hazard ratio [HR], 0.843; 95% CI, 0.814 to 0.873) and nonrecent immigrants (HR, 0.902; 95% CI, 0.876 to 0.928) compared with nonimmigrants. Cancer-specific mortality was also lower for recent immigrants (HR, 0.857; 95% CI, 0.823 to 0.893) and nonrecent immigrants (HR, 0.907; 95% CI, 0.875 to 0.94). Among immigrants, each year from the original landing was associated with increased mortality (HR, 1.004; 95% CI, 1.000 to 1.009) and a trend to increased cancer-specific mortality (HR, 1.005; 95% CI, 0.999 to 1.010).

Conclusion — Immigrants demonstrate a healthy immigrant effect, with lower cancer-specific mortality compared with Canadian-born individuals. This benefit seems to diminish over time, as the survival of immigrants from common cancers potentially converges with the Canadian norm.