Stage-Specific Risk of Breast Cancer among Canadian Immigrant and Non-Immigrant Women

Background: Breast cancer screening utilization varies across immigrant and non-immigrant populations. Recent studies have also suggested that some immigrant populations in Canada present with a higher frequency of later-stage breast cancer compared to non-immigrants. Our study aimed to augment prior research by presenting breast cancer stage distributions and stage-specific breast cancer incidence rates for immigrant and non-immigrants in British Columbia, Canada. Methods: We utilized a population-based cohort of more than 1.3 million women built from linked administrative health and immigration data sets. Age-standardized incidence rate ratios were generated to compare immigrant and non-immigrant groups. Poisson regression was used to assess the relative frequency of later stage diagnosis among immigrant groups compared to non-immigrants. Results: Indian and Chinese immigrants both showed significantly lower stage I and stage II-IV incidence rates compared to non-immigrants. However, Indian immigrants showed a higher frequency of later stage tumours at diagnosis compared to non-immigrants, while in contrast Chinese immigrants showed a lower frequency of later stage tumours. Filipino immigrants showed similar stage-specific rates and stage at diagnosis compared to non-immigrants. Conclusions: Our findings highlight a need for continued surveillance of cancer among immigrant and non-immigrant populations and inquiry into reasons for differences in stage at diagnosis across groups.