Over the past three decades, incidence rates of colorectal cancer in people younger than 50 years have doubled worldwide; about 10% of all new cases are now diagnosed in younger adults. This rising burden contrasts with decreasing rates in older adults, suggesting that new, as-yet unidentified, environmental or lifestyle factors may be driving disease in younger populations.
The ECCE project focuses on the gut microbiome as a potential key contributor. The microbiome is established early in life and is shaped by factors such as birth mode, diet, breastfeeding, and antibiotic exposure. Its composition varies across regions; in industrialized countries, it has higher levels of bacteria capable of producing DNA-damaging compounds.
The central hypothesis is that an increase in the prevalence of these mutagen-producing bacteria in the microbiomes of children over recent decades has led to higher mutational burdens in normal colorectal tissue early in life, ultimately contributing to the global rise in the incidence of early-onset colorectal cancer.
Incidence rates of colorectal cancer in individuals younger than 50 years have risen sharply over the past three decades in European countries and other high-income countries. This represents an urgent and growing public health challenge. Despite this alarming trend, its underlying causes remain largely unknown, limiting effective prevention strategies.
Colorectal cancer, which affects the colon and rectum, is one of the most common and lethal cancers worldwide. There are striking geographical variations in incidence. Colorectal cancer is particularly common in high-income regions such as Europe, North America, Australia, and parts of East Asia, whereas it is less common in many regions of Africa, South America, and South-East Asia. Established risk factors include ageing, obesity, smoking, alcohol consumption, and certain dietary patterns. However, these factors do not fully explain the rapid rise in early-onset colorectal cancer observed in recent decades. This suggests that additional, as-yet unidentified, environmental and biological drivers are involved.
Early-onset colorectal cancer, typically defined as colorectal cancer diagnosed before age 50 years, has emerged as a major and concerning global public health trend over the past three decades. Unlike late-onset disease, early-onset colorectal cancer is increasing in incidence in many high-income countries, including in Europe, North America, and parts of Asia, while the underlying causes remain incompletely understood. Although traditional risk factors such as obesity, diet, alcohol consumption, and smoking may contribute, they do not fully explain the rapid and sustained rise in incidence in younger populations, suggesting the involvement of additional environmental, microbial, and early-life exposures. Clinically, early-onset colorectal cancer is often diagnosed at more advanced stages and can present with more aggressive disease characteristics, partly due to delayed recognition in younger individuals who are not considered to be at risk. This shifting epidemiology highlights an urgent need to identify novel causal mechanisms, improve early detection strategies, and develop targeted prevention approaches specifically addressing younger populations.