The incidence of colorectal cancer is decreasing among older adults, primarily due to increased screening. But researchers are seeing an alarming change in younger people, with more cases now occurring in adults under 50, including people in their 30s. A new national study conducted in Switzerland found that while the number of diagnoses in this age group has steadily increased in recent decades, younger patients are more likely to receive a terminal diagnosis.
The study was led by scientists from the University of Geneva (UNIGE) and the University Hospitals of Geneva (HUG). Published in european cancer journalThe study analyzed approximately 100,000 colorectal cancer cases recorded in Switzerland over a 40-year period. The findings represent a growing public health concern and highlight the need to increase awareness of early warning signs.
Colorectal cancer incidence increases among younger people
Colorectal cancer is currently the third most commonly diagnosed cancer and the second leading cause of cancer death worldwide. According to the World Health Organization, more than 1.9 million new infections were reported worldwide in 2022, resulting in nearly 900,000 deaths.
The highest incidence of colorectal cancer is in Europe, Australia, and New Zealand, and the highest mortality rate from colorectal cancer is in Eastern Europe.
In Switzerland, colorectal cancer ranks among the three most common cancers in the country, with approximately 4,500 new cases diagnosed each year. Researchers say that while testing programs have helped reduce the number of infections among adults over 50, the opposite trend is occurring among younger age groups in many wealthy countries.
“We are now seeing cases emerging in people in their 30s with no personal or family history of the disease. Diagnosis in these patients is often delayed, by which time metastases are already present,” explains Dr. Jeremy Meyer, a resident physician in the UNIGE Faculty of Medicine Department of Surgery and a senior consultant surgeon in the HUG Department of Gastrointestinal Surgery.
Swiss study tracks 40 years of cancer data
Professor Meyer, in collaboration with epidemiologist Dr. Evelyn Fournier from the UNIGE Geneva Cancer Registry, conducted the first Swiss national study focusing specifically on early-onset colorectal cancer.
Researchers looked at 96,410 patients with colorectal cancer diagnosed from 1980 to 2021. Data were obtained from the Geneva Registry and the National Cancer Registry, which compiles information from cantonal cancer registries across Switzerland.
The study found that cancers diagnosed before age 50 accounted for 6.1% of all colorectal cancer cases. In young adults, the incidence increased by approximately 0.5% per year, eventually reaching nearly 7 cases per 100,000 person-years.
This increase is in sharp contrast to the decline seen in adults aged 50 to 74, the most common age group targeted for screening. In that group, it fell by 1.7% for men and 2.8% for women.
“Our study also shows that the observed increases are primarily for rectal cancer in men and women, and right-sided colon cancer in young women. These differences suggest the existence of distinct biological or environmental mechanisms,” says Evelyn Fournier.
Researchers also found that younger adults were more likely to have advanced cancer at the time of diagnosis. Approximately 20% of patients younger than 50 years already had metastatic disease at the time of diagnosis, whereas patients younger than 50 years already had metastatic disease.
Warning signs and early screening
The research team says increased awareness of the symptoms of colorectal cancer could lead to earlier detection. Persistent abdominal pain, blood in the stool, unexplained weight loss, and persistent changes in bowel habits should not be ignored, especially in young adults who think they are too young to develop the disease.
“Some countries, such as the United States, have chosen to lower the age for screening to 45 years. Screening should occur even earlier in cases of increased familial risk or hereditary colorectal cancer,” says Jeremy Meyer.
Researchers are still trying to understand why colorectal cancer is increasing in younger people. Possible factors include changes in diet and lifestyle, rising obesity rates, and environmental exposures early in life that can influence the gut microbiome. However, scientists say there is still no single explanation that fully explains this trend.
