The authors of a new Lancet paper suggest shifts in diet and physical activity may be a factor.
The number of people under 50 years being diagnosed with bowel cancer is rising globally, with Australia reporting the highest rate of early-onset bowel cancer among 50 countries, according to new international research.
Over the past five years, the highest rates of early-onset colorectal cancer (in younger adults) were found in Australia (16.5 per 100,000), the US at 15.2, New Zealand at 14.8, the USA at 14.8, and South Korea at 14.3.
For older adults, the highest rates were in the Netherlands (168.4), Denmark (158.3), Japan (156.0), Spain (148.2), and Croatia (146.8). The lowest rates were seen in India, Uganda, Costa Rica and Ecuador for both age groups.
The findings, published in The Lancet Oncology, revealed that the increase in CRC rates among young adults was no longer limited to high-income countries, but has also been observed in some low-income countries in Asia, Latin America and the Caribbean.
Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer death, with over 1.9 million new cases and nearly 904,000 deaths worldwide in 2022. The study aimed to analyse global CRC rates in younger adults (ages 25-49 years) versus older adults (ages 50-74 years) using a decade of data up to 2017 from 50 countries.
The authors emphasised that the reasons behind the rise in CRC rates among young adults remained largely unclear. They suggest that changes in diet—shifting from low-fat, high-fibre foods to increased consumption of red and processed meats, sugars and convenience foods—along with more sedentary lifestyles tied to economic growth in high-income countries may contribute to this generational shift in CRC rates. However, further research was needed to confirm these factors.
“Key determinants, however, remain elusive and are likely to differ, given the diverse social contexts and the extent to which economic growth influences major colorectal cancer risk factors, such as diets, physical inactivity, and obesity, across populations,” the authors wrote.
“Previous studies have noted that the rising incidence of colorectal cancer in several Latin American countries coincided with the economic liberalisation and globalisation of food systems in the late 1980s to early 1990s and subsequently with the pronounced obesity epidemic that affected all ages.
“For instance, from 1990–2022, the obesity prevalence among children (aged 5–19 years) increased from 6–7% to 22–33% in Chile and from 3% to 19–22% in Argentina, larger than the rise from 11–12% to 19–22% in the USA.
“Evidence from a US-based prospective cohort study of women suggested that each 5-unit increase in BMI measured at age 18 years was associated with a 20% increased risk of early-onset colorectal cancer.
“Meanwhile, a substantially lower prevalence of obesity in Japan and neighbouring east Asian countries suggests factors beyond bodyweight. A considerable shift from traditional diets, rich in low-fat and high-fibre foods, to increased consumption of red or processed meat, sugars, and ultra-processed convenience foods has probably contributed, at least in part.
“Between 1961 and 2021, South Korea and Japan saw a dramatic increase in meat intake, with a 19-times increase in South Korea and seven-times increase in Japan.”
While successful CRC screening programs are thought to explain the decline in rates among older adults in some countries, the rising CRC incidence among younger adults could eventually lead to higher rates among older populations, potentially reversing the progress made in reducing the disease.
The authors stressed the importance of global efforts to better understand these trends and to raise awareness of CRC’s unique symptoms, aiming to improve early detection and reduce CRC rates in young adults.
“The increase in early-onset colorectal cancer, previously seen predominately in high-income western countries, has now been documented in various economies and regions worldwide, marking it as a global phenomenon,” they concluded.
“The global reach of this alarming trend calls for innovative tools to prevent and control cancers linked to nutritional attributes, physical inactivity, and excess bodyweight, which might be more challenging to address than the tobacco epidemic.
“There is an urgent need for global initiatives and cross-country partnerships to identify the causes of early-onset colorectal cancer and implement effective preventive strategies that align with local resources and culture. Educational efforts to increase awareness of the increase in the incidence of early-onset colorectal cancer and its unique symptoms, especially among primary care providers, would have far reaching effects in reducing delayed diagnoses and mortality.”
In June this year the National Bowel Cancer Screening Program was expanded to include people aged 45 years and older, who choose to opt in to have a screening kit sent to them every two years.
As reported in Gut Republic, the changes to the program came as bowel cancer rates continue to increase in younger people around the world and followed updated guideline recommendations made last year.
Australians aged 45–49-year-olds can join 50–74-year-olds in being able to request a free test kit through their GP, rather than having to contact the registry directly.
Those in the 40-44 age group still fall outside the national screening program, but GPs can refer them for a pathology screening test which attracts a Medicare rebate. Anyone can purchase a test kit from a pharmacy for around $40.
A free screening kit will continue to be automatically posted out every two years for those aged 50-74 years.
