While declining in people over 50, colorectal cancer is increasing worryingly among younger individuals, sometimes as early as their thirties. A team from the University of Geneva (UNIGE) and the Geneva University Hospitals (HUG) has published the first study on this trend at the Swiss level.
Based on an analysis of nearly 100,000 cases over 40 years, it highlights an annual increase of 0.5% within this population. Published in the
European Journal of Cancer, this research also sheds light on late diagnoses and calls for greater awareness.
Ranked third in incidence and second in mortality, colorectal cancer is among the most common cancers worldwide. According to World Health Organization estimates, over 1.9 million new cases were diagnosed in 2022, with nearly 900,000 deaths. The highest incidence rates are observed in Europe, Australia, and New Zealand, while Eastern Europe records the highest mortality levels.
In Switzerland, the disease is also among the three most common cancers, with approximately 4,500 new cases diagnosed each year. While cases are declining in people over 50 — thanks in part to the expansion of screening programs — they are increasing worryingly among younger individuals. This trend is observed in many high-income countries.
Nearly 28% of patients under 50 have metastatic disease at the time of diagnosis.
"We are now seeing cases appearing as early as the thirties, with no personal or family history. These patients are unfortunately often diagnosed late, when metastases are already present," explains Dr. Jeremy Meyer, privat-docent at the Department of Surgery of the UNIGE Faculty of Medicine and senior attending physician at the HUG Visceral Surgery Service.
Steady increase
The researcher, in collaboration with Dr. Evelyne Fournier, epidemiologist at the
Geneva Tumor Registry hosted at UNIGE, conducted the first national study on this phenomenon. The analysis covers 96,410 cases diagnosed between 1980 and 2021. These data come from the Geneva registry as well as the
National Cancer Registration Agency, responsible for centralizing and analyzing information from cantonal registries.
The study results show that cancers occurring before age 50 represent 6.1% of all cases. In this population, incidence has increased steadily, with an annual progression of about 0.5%, reaching nearly 7 cases per 100,000 person-years. This trend contrasts sharply with the decline (-1.7% for men and -2.8% for women) observed in the age group eligible for screening, i.e., 50-74 years.
Histological section of colorectal cancer.
© Laura Rubbia-Brandt
"Our study also shows that the observed increase mainly concerns rectal cancers in both men and women, as well as right-sided colon cancers in young women. These differences suggest the existence of distinct biological or environmental mechanisms," says Evelyne Fournier. Finally, this work shows that nearly 28% of patients under 50 have metastatic disease at the time of diagnosis, compared to about 20% of older patients.
Towards earlier screening?
The research team emphasizes the importance of raising awareness of suggestive symptoms, such as persistent abdominal pain, blood in the stool, changes in bowel habits, or unexplained weight loss. These signs should not be downplayed and should lead to a medical consultation.
"Some countries, such as the United States, have chosen to lower the starting age for screening to 45. In cases of increased family risk or hereditary colorectal cancer, screening should be performed even earlier," says Jeremy Meyer.
Several factors may contribute to this increase, including changes in diet and lifestyle, rising obesity rates, or early environmental exposures affecting the gut microbiota. However, at this stage, no single cause can explain the phenomenon.