Population-level outcomes for screening program cancers in First Nations people in Ontario, Canada

Importance — Understanding trends among screening program cancers (breast, cervical, and colon) equips researchers, policymakers, and First Nations communities with evidence to inform cancer system improvements.

Objective — To examine cancer incidence, mortality, and survival trends for screening program cancers among First Nations people in Ontario, Canada, compared with other Ontario residents.

Design, setting, and participants — This retrospective cohort study examined incidence (1994-2018), mortality (1994-2017), and survival (2007-2019) of breast, cervical, and colon cancers among First Nations people identified from the Indian Registry System linked to the Registered Persons Database and other Ontario residents identified from the Registered Persons Database.

The data were analyzed between July 2020 and March 2022.

Main outcomes and measures — Baseline characteristics between the First Nations and other Ontario cohorts were compared. Negative binomial regression adjusting for age and sex was used to model annual incidence and mortality. Crude rates were plotted using 3-year moving averages. Cox proportional hazards regression, adjusting for age, sex, comorbidity, and cancer stage, was used to model survival. Interactions were tested for all models.

Results — The largest annual cohort included 146 498 First Nations people (median [IQR] age, 41 [28-55] years; 50.7% male) and 1 1840 783 other Ontario residents (median [IQR] age, 48 [33-62] years; 51.1% female). Compared with other Ontario females, First Nations females had lower breast cancer incidence (rate ratio [RR], 0.77 [95% CI,0.73-0.82]) and mortality (RR, 0.79 [95% CI, 0.70-0.90]). Cervical cancer incidence and mortality were higher in First Nations females (RR, 1.47 [95% CI, 1.23-1.70] and 2.26 [95% CI, 1.78-2.88], respectively); however, overtime, both rates declined more rapidly among First Nations females. Colon cancer incidence was higher for First Nations people; those aged 40 to 49 years had a similar elevated risk to those aged 50 to 74 years (incidence RR, 1.27 [95% CI, 1.06-1.51] and 1.29 [95% CI, 1.20-1.40], respectively). First Nations people had higher colon cancer mortality (RR, 1.18 [95% CI, 1.07-1.31]). Once diagnosed, First Nations people were more likely to die compared with other Ontario residents (breast cancer: hazard ratio, 1.51 [95% CI,1.28-1.76]; cervical cancer: hazard ratio, 1.60 [95% CI, 1.12-2.27]; colon cancer: hazard ratio, 1.19 [95% CI, 1.07-1.32]).

Conclusions — This cohort study of First Nations people in Ontario and other Ontario residents suggests that clear disparities persist despite progress over time. Cancer prevention, screening programs, and care systems for Indigenous peoples in Ontario need optimization.