Doctors worldwide are alarmed by the rising number of under‑50s developing colorectal cancer, and a historic collection of tumours could finally help show why this is happening.
Old tumours, new clues
At St Mark’s Hospital in London, pathologists have stored bowel cancer samples for decades, carefully sealed in blocks of wax. For years they were mainly teaching tools. Now, they are being treated as a time capsule.
Researchers are extracting DNA from tumours removed in the 1950s and comparing them with cancers diagnosed in young adults today. Back then, colorectal cancer in people under 50 was rare. Today, it is one of the fastest‑rising cancers in that age group across several high‑income countries.
Michael Schumacher, the new separation
The team is searching for genetic “signatures” in the cancer cells. These are tiny patterns of damage written into the DNA by different environmental exposures. The concept, known as the exposome, pulls together everything the body encounters over a lifetime: diet, pollution, tobacco, alcohol, stress, chemicals and even microplastics.
The key question: do tumours in young adults today carry marks that did not exist in cancers from the mid‑20th century?
What the exposome might reveal
Modern life looks nothing like life in the 1950s. Our food is more processed, our jobs are more sedentary, and our contact with synthetic chemicals is constant. Researchers suspect these changes are quietly reshaping the colon.
- High intake of ultra‑processed foods and sugary drinks
- Low fibre diets lacking whole grains, fruit and vegetables
- Long hours sitting at desks or screens
- Greater exposure to air pollution and microplastics
- Alcohol consumption starting earlier in life
Each of these factors may cause subtle irritation, inflammation or damage to cells in the bowel. Over years, that damage can accumulate. If the DNA in those cells breaks and repairs in the wrong way, cancer can emerge.
The suspicion is not that one single lifestyle factor is to blame, but that decades of combined exposures are pushing cancers to appear earlier and progress faster.
Preliminary work in other studies has suggested that early‑onset colorectal cancers can behave more aggressively than those in older adults. Tumours may grow more rapidly, or spread before they are detected. Understanding whether modern environmental pressures are driving that behaviour could shape prevention campaigns and future treatments.
Why more young adults are getting screened
The shifting age profile of colorectal cancer has already forced a rethink of screening guidance. In the United States, national recommendations now suggest that average‑risk adults start screening at 45 instead of 50.
Data published in the medical journal JAMA shows that screening rates among 45‑ to 49‑year‑olds have climbed in recent years, with over a third now up to date. That is a clear step forward, but the benefits are not shared equally.
| Group | Screening uptake trend (45–49 years) |
|---|---|
| Insured, higher education | Sharp increase, above one‑third screened |
| Uninsured or lower income | Much lower uptake, screening often delayed |
People with health insurance and higher education levels are far more likely to undergo colonoscopies or stool tests. Those without stable access to healthcare often miss out, leaving cancers undetected until they cause serious symptoms.
Screening can identify and remove tiny growths, known as polyps, long before they turn cancerous, cutting the risk of dying from the disease.
Yet many people in their 30s and 40s do not realise they could be at risk at all. The disease is still widely seen as something that happens after retirement, not during the years of building a career or raising children.
Warning signs young adults tend to ignore
Doctors report that younger patients often present late because early symptoms feel easy to brush off or blame on stress, diet or haemorrhoids. Signals that should trigger a medical visit include:
- Blood in the stool or on toilet paper
- Persistent change in bowel habits lasting more than a few weeks
- Unexplained abdominal pain or cramping
- Unintentional weight loss or fatigue
- A feeling that the bowel does not empty fully
These signs do not always mean cancer, but they should not be ignored, especially if they persist or worsen. Early diagnosis usually leads to much better outcomes.
Lifestyle under scrutiny
The surge in early‑onset colorectal cancer cannot be fully explained by classic risk factors like smoking, heavy drinking or strong family history. That mismatch is one reason research groups are so interested in the St Mark’s samples.
Researchers are particularly focused on three interconnected areas: diet, physical activity and the gut microbiome. The microbiome is the vast community of bacteria, viruses and other microbes that live in the intestines.
The balance of microbes in the gut can influence how food is broken down, how inflammation is controlled and how substances that contact the bowel lining are processed.
Diets high in red and processed meat and low in fibre may favour microbes that create more potentially harmful by‑products. These chemicals can irritate the bowel lining or interfere with how cells repair DNA damage.
On the other hand, diets rich in whole plant foods encourage bacteria that produce short‑chain fatty acids, which can help keep the colon lining healthy. When researchers compare tumour DNA from the 1950s with today’s, they may see hints of how this microbial shift has played out over time.
From lab findings to prevention
If scientists can link specific patterns of DNA damage to particular exposures, public health advice could become far more targeted. Instead of broad slogans about “healthy lifestyles”, messages could address concrete behaviours shown to be linked with early‑onset disease.
- Encouraging regular movement breaks during long sedentary workdays
- Shifting snacks from packaged, ultra‑processed products to simpler options
- Promoting fibre intake with whole grains, pulses, fruit and vegetables
- Highlighting the cumulative effect of even moderate drinking over decades
Some researchers also anticipate that tumour signatures might help doctors separate cancers that are likely tied to inherited genetic syndromes from those shaped mainly by environment. That distinction could guide how aggressively a patient’s relatives are screened.
What terms like “early‑onset” and “exposome” really mean
Two phrases appear frequently in discussions about this trend: early‑onset colorectal cancer and exposome. Both carry specific meanings that shape how researchers think.
Early‑onset colorectal cancer generally refers to cancers diagnosed before the age of 50. This group often includes people with no strong family history, who previously would not have been considered high risk. Patterns in this age band can signal changes in the broader environment rather than just genetics.
The exposome is a more technical idea. It captures every non‑genetic influence a person experiences from conception onwards: what they eat, breathe and touch; the social stress they face; the medicines they take. It treats the environment almost like a second genome, constantly interacting with our DNA.
Looking at 70‑year‑old tumours is a way of reading an older chapter of the exposome and comparing it with the chapter we are writing now.
By stitching together these chapters, scientists hope to see how long‑term trends in food production, chemicals, urban design and work patterns are being reflected in our bodies.
What this might mean for everyday life
While researchers analyse old samples in the lab, individuals and families are left wondering what they can realistically change. No lifestyle shift can guarantee protection, but several actions consistently show benefits for bowel health.
- Scheduling screening when you reach the recommended age in your country
- Not dismissing persistent bowel changes, even if you feel “too young” for cancer
- Aiming for regular physical activity, including simple habits like walking to work or using stairs
- Gradually cutting down on ultra‑processed foods and processed meats
- Adding fibre from oats, beans, lentils, nuts, fruit and vegetables
These are small decisions repeated over many years, rather than dramatic overnight transformations. The very idea behind the exposome is that health is shaped by thousands of tiny exposures, not just one big event.
As analysis of those mid‑century tumours progresses, the results may sharpen advice and lead to earlier, smarter screening strategies for younger adults. For now, the jars sitting on shelves at St Mark’s remind researchers that today’s choices will also be preserved in tissue, waiting for future scientists to read the marks our era has left behind.
