A Growing Threat: Young-Onset Colorectal Cancer

March is Colorectal Cancer Awareness Month, a timely reminder to challenge one of the most persistent myths about this cancer. When most people think of colorectal cancer, they picture a condition that affects older adults, typically those over 60 years old. For decades, that assumption was largely correct.

However, recent evidence shows a clear shift: colorectal cancer cases are rising among younger adults aged under 50 years old, and Hong Kong is part of this global trend. Understanding colorectal cancer symptoms, knowing your risk, and getting timely colorectal cancer screening could save your life.

A Global Wake-Up Call: Colorectal Cancer Is Getting Younger

A landmark study published in 2025 in the medical journal Lancet Oncology examined colorectal cancer trends across 50 regions and countries. The burden of colorectal cancer remained substantial in population over 50 years old. However, notably, rates of early-onset (younger than 50 years old) colorectal cancer were found to be rising in 27 of 50 regions analysed.  

Top 6 countries with highest incidence of colorectal cancer in older population (50-74 years old)

1. Netherlands
2. Denmark
3. Japan
4.  Spain
5. Croatia
6. Norway

Top 6 countries with highest incidence of colorectal cancer in younger population (25-49 years old) 

1. Australia
2. New Zealand
3. United States
4. South Korea
5. Japan
6. Canada 

Researchers suspect increasing obesity, changes in dietary patterns (more ultraprocessed foods, less whole foods and fiber), and more sedentary lifestyles (less physical activity) are contributing factors behind the rise in young onset colorectal cancer.

Colorectal Cancer Symptoms: The Red Flags You Shouldn't Ignore

One of the most dangerous aspects of young-onset colorectal cancer is that it is frequently diagnosed at a more advanced stage. Colorectal cancer symptoms can overlap with those of inflammatory bowel disease, hemorrhoids or irritable bowel syndrome (IBS), leading to diagnostic delays. 

A case-control study of more than 5,000 early-onset colorectal cancer cases identified four red-flag signs and symptoms that were significantly associated with increased risk of colorectal cancer diagnosis in adults under 50:

• Rectal bleeding: 5.13-fold increased risk

• Iron deficiency anaemia: 2.07-fold increased risk

• Diarrhoea: 1.43-fold increased risk

• Abdominal pain: 1.34-fold increased risk

It is important to note these symptoms are common and do not necessarily indicate cancer; however, appropriate medical evaluation is advisable if they occur. 

Colonoscopy in Hong Kong: A Powerful Prevention Tool

Colonoscopy is the gold standard for both the detection and prevention of colorectal cancer. The evidence supporting colonoscopy is robust and the benefits include

Benefit 1: Early Detection of Precancerous Polyps

Most colorectal cancers develop from precancerous polyps called adenomas or serrated lesions, which can take years to become malignant. During a colonoscopy, these polyps can be found and removed immediately, effectively stopping cancer before it starts.

Benefit 2: Significant Reduction in Cancer Incidence and Mortality

Studies have shown removing adenomatous polyps by colonoscopy reduces colorectal cancer risk by as much as 76–90%. Another study showed a 53% reduction in mortality following colonoscopic polypectomy. 

Colonoscopy is currently the most comprehensive method for examining the lower digestive tract. Using a flexible scope, the colon can be thoroughly inspected, and biopsies taken and polyps removed. A typical procedure takes 30 to 60 minutes.

Colorectal Cancer Screening: When Should You Get Checked?

If there are no digestive symptoms, colorectal cancer screening is suggested to start at 45-50 years old by methods like stool testing or colonoscopy. Earlier screening could be needed in high-risk individuals, specifically those with a family history of colorectal cancer. Also, if you have a history of precancerous polyps, surveillance colonoscopy is usually advised. If you are unsure which category applies to you, speak with your doctor to find out the right colorectal cancer screening plan.

Take Action Against Colorectal Cancer

Colorectal cancer is affecting more younger adults, and late diagnosis can lead to poorer outcomes. Colorectal cancer is preventable, and treatable when found early. This Colorectal Cancer Awareness Month, stay aware of symptoms and prioritise screening. 

Dr John Chi To Wong

Gastroenterology & Hepatology

• LMCHK

• MD (Alberta, Canada)

• FRCPC (Internal Medicine)

• DABIM (Ge)

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References

1. Sung, H., et al. (2024). Colorectal cancer incidence trends in younger versus older adults: an analysis of population-based cancer registry data. The Lancet Oncology, [online] 26(1). doi: https://doi.org/10.1016/s1470-2045(24)00600-4.
2. Chambers, A.C., et al (2025). Early onset colorectal cancer. BMJ, [online] 389, p.e082452. doi: https://doi.org/10.1136/bmj-2024-082452.
3. Fritz, C.D.L., et al. (2023). Red-flag Signs and Symptoms for Earlier Diagnosis of Early-Onset Colorectal Cancer. JNCI: Journal of the National Cancer Institute, 115(8). doi: https://doi.org/10.1093/jnci/djad068.
4. National Library of Medicine, (2025) Colonoscopy. Retrieved 6 March 2026 from https://www.ncbi.nlm.nih.gov/books/NBK559274/
5. Winawer, S.J., et al. (1993). Prevention of Colorectal Cancer by Colonoscopic Polypectomy. New England Journal of Medicine, 329(27), pp.1977–1981. doi: https://doi.org/10.1056/nejm199312303292701.
6. Zauber, A.G., et al. (2012). Colonoscopic Polypectomy and Long-Term Prevention of Colorectal-Cancer Deaths. New England Journal of Medicine, [online] 366(8), pp.687–696. doi: https://doi.org/10.1056/nejmoa1100370.
7. Department of Health, (2018) Common screening tests. Retrieved 6 March 2026 from https://www.colonscreen.gov.hk/en/public/about_crc/common_tests_for_crc_screening.html