Impact of Newly Introduced Population-based Screening and the COVID-19 Pandemic on Colorectal Cancer Incidence and Characteristics – retrospective cohort study

Introduction: In Hungary, population-based colorectal cancer (CRC) screening was introduced shortly before the onset of COVID-19 pandemic. We aimed to assess the combined impact of these two factors on the incidence and characteristics of CRC. Methods: The retrospective cohort study included all patients with newly diagnosed CRC between 2014 and 2023 and divided into pre-pandemic with screening (2015-2016, 2019), pre-pandemic without screening (2014, 2017-2018), pandemic (2020–2021), and post-pandemic (2022–2023) subgroups. CRC incidence, diagnostic patterns, and tumor stage were compared across subgroups. Results: Crude CRC incidence in institution’s care area was lower during pandemic (102.51 per 100,000) compared with the pre-pandemic with screening (117.92 per 100,000; p=0.060) and post-pandemic (120.60 per 100,000; p=0.044) subgroups. Age-standardized incidence differed significantly only between the pre-pandemic with screening and pandemic subgroups (125.30 vs. 105.88 per 100,000; p<0.001). During pandemic, the proportion of early-stage (AJCC 0–I) cancers was significantly reduced compared with the pre-pandemic with screening subgroup (18.74% vs. 25.08%; p=0.048) and the proportion of T1 cancers was also lower compared with the post-pandemic subgroup (6.90 vs. 12.2%; p=0.026). During pandemic, both the annual number of colonoscopies (2,706.00) and the mean number of colonoscopies required to detect one CRC (15.56) were markedly lower compared with the pre-pandemic with screening (4,590.67 and 13.97), pre-pandemic without screening (3,824.33 and 10.67), and post-pandemic (4,573.50 and 15.50) subgroups. Conclusions: The COVID-19 pandemic was associated with unfavorable changes in CRC epidemiology. Organized screening may have mitigated the negative impact during the pandemic and post-pandemic periods.