Early-onset colorectal cancer: epidemiology, risk factors, and implications for clinical practice.

The incidence of colorectal cancer (CRC) in individuals under 50 years of age has increased steadily over the past two decades in several high-income countries, contrasting with declining rates in older populations following the implementation of screening programmes. This epidemiological shift represents an emerging challenge for clinical practice and public health systems. This clinical review aims to summarise current epidemiological evidence, risk factors, and biological characteristics of early-onset colorectal cancer, and to examine its implications for screening strategies and health policy. Although hereditary cancer syndromes account for a minority of cases, most earlyonset CRCs occur in individuals without a recognised genetic predisposition. Identified risk factors include obesity, unhealthy dietary patterns, physical inactivity, microbiome alterations, and early-life environmental exposures. Diagnostic delays are common, as symptoms such as rectal bleeding or changes in bowel habits are frequently attributed to benign conditions in younger adults, leading to presentation at more advanced stages. Growing epidemiological data and modelling studies support lowering the age of average-risk screening initiation to 45 years, a strategy already adopted in several countries. However, implementation requires careful consideration of healthcare capacity, cost-effectiveness, and equitable access. Early-onset colorectal cancer represents a significant and evolving public health concern. Enhanced clinical vigilance in symptomatic young adults, together with evidence-based adjustments to screening policies, will be essential to mitigate the increasing burden of disease in this population.