The Changing Global Epidemiology of Early-Onset Colorectal Cancer: Incidence Trends, Modifiable Risk Factors, and Future Burden Projections

Early-onset colorectal cancer (EOCRC), defined as colorectal cancer diagnosed before age 50, has become an increasing global public health concern. Incidence rates have risen among younger adults in many countries, despite stable or declining rates in older populations. This review examines global EOCRC epidemiology, potentially modifiable risk factors, and projected future disease burden. Evidence from international cancer databases, population-based registries, and observational studies is synthesised, considering differences by age, sex, geographic region, and tumour location. Key risk factors include obesity, metabolic dysfunction, dietary patterns, physical inactivity, alcohol consumption, tobacco use, antibiotic exposure, and gut microbiome alterations. The review also evaluates temporal trends and projections of incidence, prevalence, and mortality. Although increasing incidence may reflect changing lifestyles, metabolic health, environmental exposures, and other early-life risk factors, their relative contributions remain incompletely understood. Improved understanding of EOCRC epidemiology and future burden may help identify high-risk populations, guide targeted prevention strategies, inform public health policy, and support discussions on earlier colorectal cancer detection and screening.