Elucidating the Drivers for the Rising Incidence of Early-Onset Colorectal Cancer: How Ecologic Studies Could Help and What Is Next.

The incidence of colorectal cancer diagnosed before age 50, often referred to as early-onset colorectal cancer, has been increasing, whereas the overall colorectal cancer incidence has declined. Elucidating the drivers for the rising burden of early-onset colorectal cancer is a priority in cancer epidemiology and prevention. In this issue of Cancer Epidemiology, Biomarkers & Prevention, Chen and colleagues demonstrated that ecologic studies are a helpful method to reveal emerging risk factors at the population level and concluded that alcohol use might be a potential contributor to the rising incidence of early-onset colorectal cancer. Moving forward, because of the observed birth cohort effect in early-onset colorectal cancer, where younger generations have a steeper increase, hypothesis-driven investigations on emerging risk factors in recent generations, especially during early life, are warranted. Ultimately, the identified risk factors could be integrated with well-established microsimulation models of colorectal cancer, powerful tools that can simultaneously capture population-level secular changes in risk factors, relative risk estimates for each risk factor, and the natural history of colorectal cancer. This would allow us to quantitatively estimate the explained and unexplained portion of the rising incidence of early-onset colorectal cancer by calendar period and birth cohorts, and to help identify priorities in etiologic research, prevention, and early detection. See related article by Chen et al., p. 217.