Evaluating incidence and mortality trends of early-onset colorectal cancer and adenoma in Belgium

Background Colorectal cancer (CRC) incidence is rising among young adults globally, yet European data remain inconclusive. This study evaluated age- and sex-specific trends in CRC incidence, adenoma detection, and mortality in Belgium, with a focus on individuals aged 20-49 years. Diagnostic procedure trends in the 40-49 years age group were also analyzed to contextualize epidemiological patterns. Materials and methods Data from the Belgian Cancer Registry and diagnostic records from health insurance organizations were used to analyze trends in invasive CRC, in situ CRC, and adenomas and related diagnostic procedures. Mortality data were also included. Age-specific incidence rates and annual percentage changes were calculated using joinpoint regression analysis. Results Invasive CRC incidence remained stable in individuals aged 40-49 years between 2004 and 2023, whereas adenoma and in situ CRC rates increased, coinciding with increased use of fecal immunochemical tests and colonoscopy. Mortality in this age group was stable or declined. Conversely, individuals aged 30-39 years showed increasing trends in adenomas, in situ tumors, and both early- and advanced-stage CRC. Stages I-IV CRC incidence rose significantly in the 30-34 and 35-39 years age groups, with stage IV increasing by 9% and 5% annually, respectively. Adenoma incidence increased in nearly all age groups