Colorectal cancer incidence before and during the COVID-19 pandemic: a non-linear interrupted time-series analysis.

The COVID-19 pandemic affected healthcare worldwide. This study analysed age-standardised incidence rates (ASIR) of colorectal cancer (CRC) in Bavaria to assess the COVID-19 pandemic's impact. We modelled CRC ASIR, overall and in the subgroups (sex, age group, site and stage), in the pre-pandemic (01/2007 to 02/2020) and pandemic (03/2020 to 02/2022) periods using interrupted time-series analyses. Predictions for the third year of the pandemic (03/2022 to 02/2023) were compared to expected ASIR. Comparing expected and observed CRC ASIR during the first year of the pandemic showed a significant relative change of -8.8% (95% CI: -12.7% to -4.6%), improving to 1.4% (95% CI: -4.5% to 7.2%) in the third year of the pandemic. Likewise, ASIR significantly decreased across almost all subgroups during the first year of the pandemic, recovering during the second and the third year of the pandemic. Early stages showed a significant estimated reduction, persisting until the third year of the pandemic (-4.7%; 95% CI: -8.6% to -0.9%). In contrast, for women aged 70 years and above and women with colon cancer, ASIR experienced a significant excess. In the first year of the pandemic, estimated CRC ASIR experienced significant decline, returning to the expected rates during the third year of the pandemic, for most, but not all subgroups. The relative difference remained significantly negative for early stages. A significant catch-up effect occurred in the subgroups of women aged 70 years and above and women with colon cancer. Overall, estimations indicate a recovery of CRC ASIR.