Prostate cancer incidence among immigrant men in Ontario, Canada: a population-based retrospective cohort study.

Background: Prostate cancer incidence has been associated with various sociodemographic factors, such as race, income and age, but the association with immigrant status in Canada is unclear. In this population-based study in Ontario, Canada, we compared age-standardized incidence rates for immigrant males from various regions of origin with the rates of long-term residents.
Methods: In this retrospective cohort study, we linked several provincial-level databases available at ICES, an independent, non-profit research institute. We included all males aged 20 years and older in the province of Ontario eligible for health care for each fiscal year (Apr. 1 to Mar. 31) in 2008-2016. We determined age-standardized prostate cancer incidence rates, stratifying by immigrant status (a binary variable) and region of origin. We used a log-binomial model to estimate adjusted incidence rate ratios, with long-term residents (Canadian-born Ontarians as well as those who immigrated before 1985, when available data on immigration starts) as the reference group. We included age, neighbourhood income and time since landing in the models. Additional models limited to immigrant males in the cohort included immigration admission category (economic class, family class, refugee, other) and time since landing in Canada.
Results: There were 74594 incident cases of prostate cancer in the study period, 6742 of which were among immigrant males. Males who had immigrated from West Africa and the Caribbean had significantly higher incidence of prostate cancer than other immigrants and long-term residents: adjusted rate ratios of 2.71 (95% confidence interval [CI] 2.41-3.05) and 1.91 (95% CI 1.78-2.04), respectively. Immigrants from other regions, including East Africa and Middle-Southern Africa, had lower or similar incidence rates to long-term residents. Males from South Asia had the lowest adjusted rate ratio (0.47, 95% CI 0.45-0.50).
Interpretation: The age-standardized incidence rate of prostate cancer from 2008 to 2016 was consistently and significantly higher among immigrants from West African and Caribbean countries than among other immigrants and long-term residents of the province. Future research in Canada should focus on further understanding heterogeneity in prostate cancer risk and epidemiology, including stage of diagnosis and mortality, for immigrants.
Competing Interests: Competing interests: Aisha Lofters declares an operating grant paid to her institution from the Canadian Institutes of Health Research (grant no. 162506) and a paid role as provincial primary care lead, cancer screening with Ontario Health (Cancer Care Ontario). Anthony Henry is first vice president of The Walnut Foundation. Ken Noel is president of The Walnut Foundation. No other competing interests were declared.
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