Stage of colorectal cancer diagnosis for immigrants: a population-based retrospective cohort study in Ontario, Canada

Background — Colorectal cancer (CRC) is the second most common cause of cancer death in Canada. Immigrants in Ontario, Canada's most populous province, are known to have lower rates of CRC screening, but differences in stage of CRC diagnosis are not known.

Methods — We utilized linked administrative databases to compare early (stage I-II) versus late (stage III-IV) stage of CRC diagnosis for immigrants versus long-term residents among patients diagnosed in Ontario between 2012 and 2017 (n = 37,717) and examined the association of immigration-related, sociodemographic, and healthcare-related factors with stage.

Results — Almost 45% of those with CRC were diagnosed at a late stage. Immigrants were slightly more likely to be diagnosed at a late stage than their long-term resident counterparts [Adjusted relative risks (ARRs) 1.06 (95% CI 1.02-1.10)], but after adjusting for age and sex, this difference was no longer significant. In fully adjusted models, we observed a higher likelihood of late-stage diagnosis for people with the fewest co-morbidities (ARR 0.86 [95% CI 0.83-0.89]) and those with no visits to primary care (versus a high level of continuity of care) [ARR 1.07 (95% CI 1.03-1.12)].

Conclusion — Immigrants were not more likely to have a late-stage CRC diagnosis after adjusting for relevant factors, but access to primary care and healthcare contact was significantly associated with diagnostic stage.

Impact — Attachment to a primary care provider who provides regular preventive care may play a role in more favorable stage at diagnosis for CRC and thus should be a healthcare system priority.