Breast cancer incidence by country of birth among immigrant women in British Columbia, Canada

•Breast cancer incidence among women from several East Asian countries was significantly lower than among non-immigrants.•Immigrants to British Columbia from South Asian countries show lower breast cancer incidence than non-immigrant women.•There is considerable variation in risk among British Columbia immigrants according to birth country, even among those from a common world region.•Incidence patterns varied by age for several groups. For example, immigrants from the Philippines and Iran showed higher risk in ages 40-49 compared to non-immigrants and lower risk at ages 70+.•Examining incidence by birth country reveals important variation in risk that is not observable when data are aggregated at the world region level. Breast cancer rates vary internationally and between immigrant and non-immigrant populations. We describe breast cancer incidence by birth region and country in British Columbia, Canada. We linked population-based health and immigration databases for a population with >1.29 million immigrants to assess breast cancer incidence among immigrant and non-immigrant women. We report age-standardized incidence ratios (SIRs) by birth region and country using non-immigrant women as the standard. SIRs varied widely by both birth country and region. Low rates were found for South (SIR = 0.52, 95% CI: 0.47,0.59) and East Asian (SIR = 0.75, 95% CI: 0.72,0.79) women and a higher rate for Western Europeans (SIR = 1.15, 95% CI: 1.01,1.30). There is considerable variation in SIRs across some of British Columbia’s largest immigrant populations and several demonstrate significantly different risk profiles compared to non-immigrants. These findings provide unique data to support breast cancer prevention and control.