Colorectal Cancer Incidence in the US Versus Canada, Among Individuals Aged 45 to 49 Years, Following US Expansion of Screening Eligibility

Objectives: To examine the differences in colorectal cancer (CRC) incidence between the US and Canada, among individuals aged 45 to 49 years, following expansion of screening eligibility in the US. Methods: This is an ecological analysis based on publicly available data for CRC incidence in the US and Canada. US data were based on the US Cancer Statistics Public Use Research Database, while the Canadian data were based on Statistics Canada tables (which represented all Canadian jurisdictions except for Nova Scotia). Descriptive analyses for cancer incidence rates per 100,000 among individuals aged 45 to 49 years were performed for Canada versus the US, with stratification performed for age group, sex, and subsite. Subsequently, a difference-in-differences (DiD) analysis was performed to further examine the differences between the US and Canada. Results: Colorectal cancer rates per 100,000 (2016 to 2023) for individuals aged 45 to 49 years increased in Canada from 30.6 (2016) to 34 (2023), while in the US, rates increased from 34.9 (2016) to 53.1 (2023). For the US data, when calculating the percentage of localized disease out of all patients with known stages, this increased from 28.5% in 2016 to 40.8% in 2023. Furthermore, comparing US versus Canadian data and using pre- versus postexpansion policy means in both countries, DiD was 12.85 (95% CI: 10.13-15.57, P <0.001). Conclusions: Expansion of CRC screening eligibility in the US was associated with a significant increase in reported CRC incidence in the US versus Canada, among individuals 45 to 49 years old, which was principally driven by increasing rates of localized-stage diagnoses.