Bowel cancer is the fourth most common type of newly diagnosed cancer and the second most deadliest in Australia, according to Bowel Cancer Australia.

The latest Australian researchⁱ revealed 28,265 cases of aggressive types of early-onset (those aged between 20 and 49) bowel cancer over the past 30 years. That included an estimated 4,347 additional early-onset bowel cancer cases attributable to the rising rates of the disease.

An early release of findings (published in medRxiv) from a study conducted by University of Melbourne researchers examined bowel cancer rates among those aged 20 to 49 and over, across a thirty-year period (1990-2020).

It found that rising early-onset colon cancer rates resulted in 2,398 excess cases, or a 26% increase in observed cases compared to expected numbers if the increase did not occur. Similarly, rising early-onset rectal cancer rates resulted in 1,949 excess cases or a 20% increase.

Author Professor Mark Jenkins, University of Melbourne, said, “Our inability to halt the rising burden of early-onset bowel cancer over the last thirty years has resulted in over 4,300 excess cases being diagnosed among young Australians.”

“Notably, we found bowel cancer incidence was 2 to 3-fold higher among Australians born in the 1990s versus 1950s, suggesting increasing prevalence or earlier exposure to risk factors. The increase is occurring even for the most aggressive forms of the disease.

However, the underlying causes remain unknown,” lead author Aaron Meyers, University of Melbourne, added.

The Australian research further supports international research published in The Lancetⁱ, which reveals Australia now has the highest rates of early-onset bowel cancer in the world, with a faster increase found in women than in men.

The international research compared bowel cancer rates in those aged under and over 50 in 50 countries worldwide. It found early-onset bowel cancer increased in 27 of the 50 countries in the last decade until 2017, a rise no longer confined to high-income western countries.

Bowel Cancer Australia CEO, Julien Wiggins, said, “The research showed the rising incidence of early-onset bowel cancer had continued at 2 to 4% annually until 2017. However, bowel cancer rates among those over 50 were falling in many of the countries studied, including Australia.”

“In 2024, it is estimated to be the deadliest cancer for men and the second deadliest cancer for women under 50,” he added.

“This risk of being diagnosed before age 40 has more than doubled since 2000, and 1-in-9 new bowel cancer cases now occur in people under age 50.”

“As screening is not routinely offered to people at average risk under 45, we need to improve awareness among GPs and the public about the red flag signs and symptoms of early-onset bowel cancer,” Mr Wiggins said.

“This remains the primary opportunity for early detection, provided young people receive prompt colonoscopy referral to rule out bowel cancer as an underlying cause of their symptoms.”