Doctors warn colon cancer is surging in people in their 30s as it presents no immediate signs

Colon cancer has long been thought of as a disease that targets older people. A landmark new study suggests that assumption could be dangerously wrong, and it may already be too late by the time younger patients find out.

A major Swiss study analysing nearly 100,000 colorectal cancer cases recorded over four decades has found that diagnoses in adults under 50 have been steadily climbing for years, even as rates fall among older adults thanks to widespread screening programmes.

Some patients are being diagnosed in their thirties, with no family history of the disease and no obvious warning signs.

Researchers from the University of Geneva and the Geneva University Hospitals examined 96,410 colorectal cancer cases diagnosed between 1980 and 2021. They found that cancers diagnosed before the age of 50 accounted for 6.1% of all colorectal cancer cases, and that incidence rates in younger adults rose by around 0.5% per year throughout the study period.

Colon Cancer is on the rise in young people (Getty stock image)

Why is colon cancer rising in younger people?

In stark contrast, rates dropped significantly among adults between 50 and 74, the age group most commonly targeted by screening programmes. That decline was 1.7% in men and 2.8% in women.

Researchers believe possible contributing factors include changes in diet and lifestyle, rising obesity rates and environmental exposures early in life that may affect the gut microbiome.

However, scientists say there is still no single explanation that fully accounts for the trend.

Abdominal pain is a key symptom of colon cancer (Getty stock image)

What are the warning signs of colon cancer in young people?

This is where the findings become particularly alarming. Nearly 28% of patients under 50 already had metastatic disease, meaning the cancer had already spread, at the time of diagnosis, compared with around 20% of older patients.

"Cases are now emerging in people in their thirties, with no personal or family history of the disease," said Dr Jeremy Meyer, Senior Consultant Surgeon at the Geneva University Hospitals.

"These patients are often diagnosed late, by which time metastases are already present."

Warning signs that should not be ignored include persistent abdominal pain, blood in the stool, unexplained weight loss and lasting changes in bowel habits. Doctors stress that younger adults are particularly vulnerable to dismissing these symptoms, assuming they are simply too young for cancer to be a concern.

The US have updated the age where you should be screened for colon cancer to 45 (Getty stock image)

When should you get screened for colon cancer?

The research team points out that some countries have already responded to the emerging trend. The United States lowered its recommended colorectal cancer screening starting age from 50 to 45 in recent years, and researchers say those with a family history of the disease should begin screening even earlier.

In Switzerland, colorectal cancer ranks among the three most common cancers, with around 4,500 new diagnoses every year. Globally, colorectal cancer is the third most commonly diagnosed cancer in the world and the second leading cause of cancer deaths, with more than 1.9 million new cases reported in 2022 alone.

The study also found that the increase primarily concerns rectal cancers in both men and women, as well as right-sided colon cancers in young women specifically.

"These differences suggest the presence of distinct biological or environmental mechanisms," said epidemiologist Dr Evelyne Fournier, who co-led the research.