Australia is confronting a disturbing and unexplained surge in bowel cancer cases among its younger population, with new data revealing the nation now holds an unwelcome world record for the disease in people under 50.
A Startling Trend Defies Expectations
Once primarily associated with older age, bowel cancer is increasingly striking Australians in their prime. One in nine bowel cancer cases is now diagnosed in someone under the age of 50. The most alarming increase has been seen in people in their 40s, where diagnoses have skyrocketed by 41 per cent over the past two decades.
This trend stands in stark contrast to the experience of older Australians. Thanks largely to the successful National Bowel Cancer Screening Program, introduced in 2006, incidence rates for those aged 50 and over have fallen by an impressive 35 per cent over the same period.
According to the latest Australian Institute of Health and Welfare figures, the rate among 40 to 49-year-olds has climbed from 22 cases per 100,000 people in 2005 to an estimated 31 per 100,000 in 2025. An international study late last year confirmed Australia now has the highest rate of bowel cancer globally for people aged 25 to 49.
Searching for the "Smoking Gun" Behind the Rise
Medical experts are urgently working to unravel the mystery behind this rise in early-onset colorectal cancer. Cancer Australia medical director Vivienne Milch stated there is no single definitive answer, but research is intensifying.
"We are trying to work out what is the driver of that. Is it something beyond the risk factors that we already know about?" Professor Milch said. Her agency is analysing trends, funding new research, and updating guidance for GPs to help diagnose younger patients earlier.
Several potential factors are under the microscope. A major US study published in November suggested a significant link, finding that women who consumed the highest amounts of ultra-processed foods had a 45 per cent higher risk of developing pre-cancerous colorectal polyps.
Meanwhile, Melbourne scientists made a breakthrough in 2024, identifying a variant of gut bacteria E. coli that produces a toxin called colibactin, which can cause DNA damage in the bowel. University of Melbourne's Associate Professor Dan Buchanan described the discovery as finding a "smoking gun" in the search for causes.
Established risk factors like high alcohol consumption, excessive red and processed meat intake, smoking, and being overweight remain critically important. Conversely, diets rich in wholegrains, fibre, and dairy products are associated with lower risk.
Screening Success and the Challenge of Early Diagnosis
The success of the national screening program for over-50s highlights the power of early detection. The free, at-home test kit, now offered from age 45, looks for hidden blood that could indicate pre-cancerous polyps or early cancer. If positive, a follow-up colonoscopy is recommended.
However, the system faces challenges. Only 42 per cent of eligible people returned their test kit in 2022-23. Furthermore, wait times for diagnostic colonoscopies often exceed the recommended 30-day target, with Western Australia's median wait of 54 days in 2023 being the nation's shortest.
Professor Milch also pointed to inequity in colonoscopy access, with significant overuse in some metropolitan areas like Melville and underuse in regional areas like the Kimberley, diverting resources from those most in need.
For younger Australians not yet eligible for screening, awareness of symptoms is vital. Philippa Greenwood-Jones from Currambine was diagnosed at just 40 after noticing blood in her stool. Despite being fit and healthy, a colonoscopy revealed a tumour.
"With younger people, GPs tend to tell people it’s just haemorrhoids," Ms Greenwood-Jones said. "I was lucky that my GP was straight onto it." After treatment, she has since advocated for greater awareness, emphasising that finding the root cause is key to prevention.
As research continues to hunt for answers, the message for all Australians is clear: know the symptoms, understand the risk factors, and if eligible, participate in the life-saving screening program.
