Why More People in Their 30s Are Suddenly Getting Colon Cancer

A major Swiss study found that colorectal cancer is becoming increasingly common in adults under 50, even as rates decline in older age groups.

Researchers in Switzerland have identified a concerning trend: while colorectal cancer rates are declining among older adults, the disease is becoming increasingly common in younger people, including some in their thirties. Drawing on four decades of cancer data, the first nationwide study of its kind in Switzerland found a steady rise in cases among adults under 50. The findings, published in the European Journal of Cancer, also show that younger patients are often diagnosed at later stages, underscoring the need for greater awareness of symptoms and risk factors.

Colorectal Cancer Remains a Major Global Health Threat

Colorectal cancer is one of the most common cancers worldwide. It ranks third in new diagnoses and second in cancer-related deaths. According to the World Health Organization, more than 1.9 million people were diagnosed with the disease in 2022, and nearly 900,000 died from it.

The highest rates of colorectal cancer are seen in Europe, Australia, and New Zealand, while Eastern Europe experiences the highest mortality rates.

Switzerland reflects this broader burden. The disease is among the country’s three most frequently diagnosed cancers, with about 4,500 new cases reported each year. Although screening programs have helped reduce diagnoses in adults over 50, researchers say the opposite trend is emerging among younger age groups. Similar increases have been reported in many high-income countries.

“Cases are now emerging in people in their thirties, with no personal or family history of the disease. These patients are often diagnosed late, by which time metastases are already present,” explains Dr. Jeremy Meyer, privat-docent in the Department of Surgery at the UNIGE Faculty of Medicine and a Senior Consultant Surgeon in the Division of Digestive Surgery at the HUG.

National Study Tracks Rising Cancer Rates Under 50

To better understand the trend, Meyer teamed up with Dr. Evelyne Fournier, an epidemiologist at the Geneva Cancer Registry at UNIGE. Together, they conducted the first national study on colorectal cancer among younger adults in Switzerland.

The analysis examined 96,410 colorectal cancer cases diagnosed between 1980 and 2021. The information came from the Geneva registry and the National Agency for Cancer Registration, which collects and analyzes data from cancer registries across Switzerland’s cantons.

The researchers found that cancers diagnosed before age 50 accounted for 6.1% of all colorectal cancer cases. Within this younger population, incidence increased by about 0.5% each year, reaching nearly 7 cases per 100,000 person-years.

That pattern stands in stark contrast to what was observed among adults aged 50-74, the group most commonly targeted by screening programs. In that population, incidence declined by 1.7% among men and 2.8% among women.

Certain Types of Colon and Rectal Cancer Driving the Increase

“Our study also shows that the observed increase primarily concerns rectal cancers in both men and women, as well as right-sided colon cancers in young women. These differences suggest the presence of distinct biological or environmental mechanisms,” says Evelyne Fournier.

The study also found that younger patients were more likely to have advanced disease when diagnosed. Nearly 28% of people under 50 had metastatic cancer at the time of diagnosis, compared with about 20% of older patients.

Earlier Screening and Symptom Awareness

The researchers say recognizing warning signs could play an important role in improving outcomes. Symptoms such as persistent abdominal pain, blood in the stool, changes in bowel habits, and unexplained weight loss should not be dismissed and should prompt a medical evaluation.

“Some countries, such as the United States, have chosen to lower the screening starting age to 45. In cases of increased familial risk or hereditary colorectal cancer, screening should be carried out even earlier,” says Jeremy Meyer.

Scientists are still working to determine why colorectal cancer is becoming more common among younger adults. Several factors may be contributing, including changes in diet and lifestyle, rising obesity rates, and environmental exposures early in life that may affect the microbiome. However, researchers say no single explanation currently accounts for the increase.

Reference: “Rising early-onset colorectal cancer in Switzerland despite declining incidence in older adults: A nationwide population-based study, 1980–2021” by Evelyne Fournier, Robin Schaffar, Katharina Staehelin, Nine Rouxel, Frédéric Ris, Christian Toso, Jean-Louis Frossard, Elisabetta Rapiti, Thibaud Koessler, Lea Wildisen and Jeremy Meyer, 30 March 2026, European Journal of Cancer.
DOI: 10.1016/j.ejca.2026.116707