Bowel Cancer on the Rise in Younger Australians: What You Need to Know

Bowel cancer incidence in people in their 30s has increased by 137% since 2000. In Australia, approximately 15% of colorectal cancers exhibit microsatellite instability (MSI), making them responsive to immunotherapies.

Incidence and Demographics

Analysis of Omico's database shows that among bowel cancer patients referred for genomic profiling, 34% were under 50 years old, and nearly 14% were under 40.

Research from 2019 indicated a steady increase in bowel cancer rates among younger Australians, with average rates for individuals aged 50 and below increasing by 1% to 9% annually between 1982 and 2014. In contrast, rates in Australians over 50 have declined since the 1990s, attributed to screening and treatment advancements.

In 2021, there were 1,884 cases in people under 50 compared to 13,020 in those over 50.

Bowel cancer is estimated to be the fifth most commonly diagnosed cancer in Australia in 2025. Approximately one in 21 men and one in 25 women are projected to be diagnosed by age 85.

"We need to understand why this is happening. Possible factors include environmental, dietary, or genetic changes." — David Thomas, founder of Omico

Risk Factors

Approximately half of all bowel cancer cases are linked to lifestyle factors, including:

• Alcohol consumption
• Smoking
• Physical inactivity
• Diets high in red and processed meat
• Low fiber intake

Other influencing factors include genetics, inflammatory bowel disease, and older age. Overweight and obesity have been identified as major risk factors for bowel, endometrial, and post-menopausal breast cancer.

The rise in cases among younger individuals may be linked to lifestyle changes over time.

Diagnosis and Treatment

One specific subset of bowel cancers—those with microsatellite instability (MSI) —makes up to 15% of colorectal cancers. These tumors are sensitive to immunotherapies such as pembrolizumab.

Lynch syndrome, an inherited condition, accounts for approximately 3% of MSI colorectal cancers.

A case reported in the sources describes a 29-year-old man diagnosed with bowel cancer whose tumor was MSI-high. After receiving immunotherapy, he has been reported as cancer-free since January.

"Australia has the highest rate of young-onset colorectal cancer globally. It has become the leading cause of cancer death in young Australians. Yet colorectal cancer is largely preventable through the removal of precancerous polyps via colonoscopy." — Dr. Prasad Cooray, Medical Oncologist, University of Melbourne

Screening Programs

The National Bowel Cancer Screening Program provides a free at-home stool test every two years for eligible individuals, originally for those aged 50-74. Participation rates were 41.7% from 2022-2023.

Due to the rising incidence in younger populations, national guidelines now recommend screening beginning at age 45. As of July 2024, individuals aged 45-49 can request a kit through the National Cancer Screening Register.

Approximately 77,000 eligible Australians in this age group requested a kit in the first six months of the expanded program.

Individuals with a family history of bowel cancer, especially if a close relative was diagnosed under age 60, are advised to consult their GP about a screening colonoscopy.

"If you notice blood in stools, changes in bowel habits, or other persistent symptoms, consult a GP." — Dorothy Keefe, CEO, Cancer Australia

Symptoms

Early-stage bowel cancer often presents without symptoms. Potential symptoms include:

• Changes in bowel habits lasting over a few weeks
• Visible blood in stool
• Persistent abdominal pain
• Unexplained weight loss
• Anemia

Preventive Strategies

Lifestyle Modifications

• Avoiding tobacco and vaping products
• Limiting alcohol consumption
• Maintaining a healthy diet rich in whole grains, legumes, fruits, and vegetables
• Limiting processed and red meat consumption
• Engaging in regular physical activity (at least 30 minutes most days)
• Maintaining a healthy weight

Environmental Factors

• Reducing exposure to UV radiation through sun protection (sunscreen, sunglasses, hats, protective clothing, seeking shade)
• Improving indoor air quality, including replacing gas stoves
• Using air purifiers for bushfire smoke
• Reducing exposure to "forever chemicals" by replacing non-stick cookware with stainless steel, titanium, ceramic, or glass products

Medical Interventions

• Vaccination against HPV and hepatitis B
• Regular screening through stool tests and colonoscopies, which can detect and remove precancerous polyps

"There is no conclusive evidence linking stress or insufficient sleep directly to cancer risk." — Professor Anne Cust, Cancer Epidemiologist, Daffodil Centre

"Expensive, unproven supplements are not a substitute for a healthy lifestyle. Regular ejaculation may reduce the risk of prostate cancer." — Professor Declan Murphy, Peter MacCallum Cancer Centre

Research and Funding

Cancer Australia has commissioned an evidence review of early onset cancer risk factors. Additionally, $15 million in funding for research on early onset cancers has been announced.

This investment underscores the urgency of understanding why younger Australians are increasingly affected—and what can be done to reverse this troubling trend.