Why More Young People Are Getting Colon Cancer

Summary

Colorectal cancer is increasingly affecting adults under 50, often without the usual risk factors. A 2025 study found that DNA mutations linked to colibactin, a toxin produced by certain gut bacteria, are more common in early-onset cases. These mutations can start in childhood, potentially turning off critical tumor-suppressor genes and accelerating cancer development. While researchers continue to explore how exposure occurs and prevention strategies, awareness of early symptoms—like persistent bowel changes, rectal bleeding, abdominal pain, fatigue, and unintended weight loss—is crucial. Timely screenings and early detection tests remain the best defenses against this rising health concern.

Takeaways

• ⚠️ Early-onset colorectal cancer (CRC) is rising, especially in adults under 50, even without traditional risk factors.
• 🌍 At least 27 countries have reported increases in young-onset CRC, while overall CRC rates in older adults have declined in many higher-income nations.
• 🧬 A 2025 study sequenced almost 1,000 tumor samples and identified DNA mutations linked to the bacterial toxin colibactin.
• 🦠 Colibactin is a genotoxin produced by certain strains of E. coli that damages human DNA, not just bacterial DNA.
• 🔬 The mutations associated with colibactin (SBS88 and ID18) are driver mutations that spur cancer development and may occur early in life.
• 📉 These mutations can inactivate the APC tumor suppressor gene, a key player in preventing colorectal cancer.
• ⏳ Early exposure to colibactin may give young individuals a head start on developing CRC, potentially 20 years earlier than usual.
• 🧪 Scientists are investigating how children are exposed to colibactin-producing bacteria and whether lifestyle or environment plays a role.
• 🩺 Screening, such as colonoscopies, remains critical for adults 45 and older, and awareness of early symptoms is important for younger people.
• 🚨 Symptoms to watch for include changes in bowel habits, rectal bleeding, abdominal pain, fatigue, and unexplained weight loss.
• 💡 Researchers are developing early detection tests to identify colibactin-related mutations in stool samples before cancer progresses.
• 🔍 Understanding the cause of early-onset CRC is key for prevention, but actionable strategies currently focus on vigilance, screening, and research.

Q & A

What is unusual about the recent trends in colorectal cancer?

Colorectal cancer is increasingly being diagnosed in people under 50, which is unusual since it typically affects older adults. In some countries, cases among young adults have even doubled in recent decades.

Do young patients with colorectal cancer usually have traditional risk factors?

No, many young patients do not have typical risk factors such as inherited genetic mutations, making the rise in early-onset cases puzzling.

What did the 2025 study in *Nature* investigate?

The study sequenced the genomes of nearly 1,000 colorectal cancer samples from early- and late-onset cases across 11 countries to identify potential causes of early-onset cancer.

What is colibactin and why is it significant in colorectal cancer?

Colibactin is a genotoxin produced by certain E. coli strains that damages DNA. The 2025 study found a pattern of DNA mutations linked to colibactin that was more common in early-onset colorectal cancer, suggesting it may contribute to the disease.

How does colibactin damage DNA?

Colibactin causes two main types of mutations: SBS88, which swaps DNA bases, and ID18, which inserts or deletes DNA sections, causing frameshifts. These mutations can disrupt important genes like APC, a tumor suppressor.

Why is early-life exposure to colibactin concerning?

Mutations caused by colibactin may accumulate during childhood, potentially giving colorectal cancer a 'head start' and causing it to develop decades earlier than usual.

What are the key symptoms of early-onset colorectal cancer?

Symptoms include changes in bowel habits lasting more than a few days, rectal bleeding or blood in stool, urgency not relieved by going, abdominal pain, weakness or fatigue, and unintended weight loss.

What preventive measures are currently recommended?

Adults 45 and older should get screened, usually via colonoscopy. Younger individuals should be vigilant for symptoms and consult a doctor if multiple signs appear.

What are researchers doing to address early-onset colorectal cancer?

They are studying how children are exposed to colibactin-producing bacteria, developing early detection tests for colibactin-related mutations, and investigating preventive strategies.

Why might early-onset colorectal cancer become a leading cause of cancer death in young adults?

Because the number of cases in people under 50 is rising rapidly, and the disease may be developing earlier in life due to factors like colibactin exposure, it could surpass other cancers in young adult mortality by 2030.

What role does the APC gene play in colorectal cancer?

APC is a tumor suppressor gene that helps prevent cancer. Colibactin-related mutations can inactivate APC, contributing to colorectal cancer development.

How did researchers identify the DNA signature of colibactin?

They used organoid models and advanced mathematical techniques to detect a mutational signature in DNA left by colibactin, confirming its link to early-onset colorectal cancer.