Early-onset colorectal cancer across Europe: Burden, mechanisms, and health-system implications.

The incidence of early-onset colorectal cancer (EOCRC), diagnosed in individuals under 50 years, is rising across Europe, presenting a growing public health challenge distinct from later-onset disease. This review synthesizes the European landscape, revealing a heterogeneous epidemiological mosaic characterized by stark regional disparities in incidence, mortality-to-incidence ratios, and temporal trends. These patterns are shaped by a transitioning continental 'exposome', that is, the cumulative, lifelong integration of dietary, metabolic, and microbial exposures, interacting with genetic susceptibility. Clinically, EOCRC in Europe is defined by a predominance for distal tumor locations, aggressive histopathology, and a molecular profile that frequently diverges from the classic adenoma-carcinoma sequence. Organized screening programs, largely calibrated to individuals aged 50 years and above, structurally exclude this demographic, while diagnostic delays remain frequent, exacerbated by low clinical suspicion in younger adults. We discuss the dual imperative of developing risk-adapted early detection strategies for asymptomatic people under 50, while optimizing fast-track pathways for symptomatic adults under 50. Furthermore, we examine the disproportionate survivorship burden compared to late-onset CRC, which includes long-term functional morbidity, psychosocial impact, and economic toxicity. These heterogeneities in epidemiological parameters across Europe, while a challenge, offer a unique opportunity for comparative research and for informing health policy. Addressing the rising burden of EOCRC requires coordinated European action to harmonize data collection and foster translational research consortia, coupled with nationally implemented, equitable, and age-tailored prevention, early-detection, and survivorship strategies that can be informed by shared European frameworks and comparative benchmarking.