Changes in childhood cancer incidence rates and trends in Canada (2001–2023): Results from the Cancer in Young People in Canada surveillance program

INTRODUCTION: We aimed to describe trends in age-standardized incidence rates (ASIRs) of childhood cancer in Canada during 20012023 and evaluate changes in ASIRs during the COVID-19 pandemic. METHODS: Data were obtained from the Cancer in Young People in Canada surveillance system. Trends in ASIRs of childhood cancer (age 0-14 years) between 2001 and 2023 were examined using joinpoint regression to estimate annual percent changes (APCs) by demographic and diagnostic categories, with comparisons across models excluding various combinations of pandemic (2020-2022) and post-pandemic (2023) years. Interventional autoregressive integrated moving average (ARIMA) models and rate ratios (RRs) were also used to examine changes in ASIRs during the pandemic. RESULTS: The overall ASIR increased by an average of 1.39% (95% CI: 0.89, 2.39) per year from 150.33 per million children in 2001 to 182.50 in 2013, then decreased by 0.65% (95% CI: -1.82, -0.03) per year to 176.97 in 2023. The recent observed decline, beginning in 2013 for all cancers combined, was attenuated and became non-significant when diagnosis years 2020-2022 or 2021-2022 were excluded. Trend discrepancies were supported by interventional ARIMA analysis, which showed monthly ASIRs for all cancers combined in 2021 and 2022 averaged about 7.5% lower than no-pandemic counterfactuals (p-values < 0.01), and rate ratios, which indicated the overall ASIR in 2021 and 2022 were both 7% lower than the ASIR for 2013-2019 (p-values < 0.05). Trends and changes in ASIRs during the pandemic varied by type of cancer. CONCLUSION: The ASIR for all childhood cancers combined has been declining since 2013. In addition, significantly fewer childhood cancers were reported during pandemic years 2021 and 2022, followed by a rebound in 2023. Incidence rates and trends incorporating pandemic years require cautious interpretation because of the difficulty in disentangling pandemic effects from changes in cancer diagnostic criteria, registration and coding practices, and the true underlying risk of childhood cancer.