Vietnam's Colorectal Cancer Burden Grows as Genetic Studies Expose Gaps in Family Screening

22,584 diagnoses and a warning for families

Vietnam had an estimated 22,584 new colorectal cancer cases and 10,990 deaths from the disease in 2024, making it the country's third most common cancer and third leading cause of cancer death. Alongside that national burden, Vietnamese genetic studies have identified a more personal problem: finding an inherited cancer risk does not always lead patients or their relatives to seek screening.

A study published in Familial Cancer on July 30, 2023, found mutations linked to hereditary colorectal cancer syndromes in 49 of 1,632 genetic test results. More than 77% of those identified cases involved Lynch syndrome, an inherited condition that weakens the body's ability to repair damaged DNA. Yet only 44% of cases underwent further cancer screening, and 48% of their families took up genetic testing.

The consequences reach beyond the person first diagnosed. At Bach Mai Hospital in Hanoi, doctors treating a man aged 26 from Hai Phong discovered an MLH1 gene mutation after learning that several relatives had also developed colon cancer. His diagnosis prompted advice for his older brother to undergo a risk assessment and genetic testing when indicated.

Colorectal cancer develops in the colon or rectum, the final sections of the digestive tract. Age, diet, alcohol, smoking and physical inactivity contribute to risk, while inherited mutations can make surveillance necessary decades earlier. Vietnam's challenge is to connect those different risks with timely checks, especially while people still feel healthy.

What Vietnam's cancer figures show

The International Agency for Research on Cancer's Viet Nam fact sheet puts colorectal cancer at 12.7% of the country's 177,404 new cancer cases in 2024, roughly one in eight diagnoses. It accounted for 9.9% of the estimated 111,015 cancer deaths.

Men had 12,570 new colorectal cancer cases, compared with 10,014 among women. The disease ranked second among cancers diagnosed in men and third among those diagnosed in women. Across both sexes, only breast and lung cancer produced more new diagnoses.

The same dataset estimates that 56,793 people were alive after receiving a colorectal cancer diagnosis during the preceding five years, equivalent to 56.2 per 100,000 people. This measure, called five-year prevalence, helps describe the population potentially needing continuing treatment, monitoring and support.

Compared with GLOBOCAN 2022, colorectal cancer moved from fourth to third for new diagnoses in Vietnam and from fifth to third for cancer deaths. The 2024 estimates use rates from subnational cancer registries applied to the national population; deaths are estimated using incidence and models informed by registry survival data. National planning therefore depends on both these estimates and stronger local registration.

Asia carries more than half the global burden

IARC's colorectal cancer fact sheet estimates 2,041,007 new cases and 917,895 deaths worldwide in 2024. The disease ranked third for diagnoses and second for cancer deaths globally.

Asia accounted for 1,064,396 cases and 480,168 deaths, representing 52.2% and 52.3% of the respective global totals. Vietnam's burden sits within a region carrying more than half of both measures.

The IARC and American Cancer Society global cancer estimates cover 34 cancer types in 186 countries. Colorectal cancer represented 9.9% of all new cancer cases worldwide, compared with 12.7% in Vietnam, a difference of 2.8 percentage points in its share of diagnoses.

The global analysis estimates 20.6 million cancer diagnoses and 9.8 million cancer deaths across all cancer types in 2024. It projects 34.4 million new diagnoses in 2050, 67% above the 2024 total, adding urgency to prevention and earlier detection.

A diagnosis at 26 exposes a family pattern

The patient from Hai Phong, identified as N.H.L., sought care at the Institute of Nuclear Medicine and Oncology at Bach Mai Hospital after prolonged abdominal pain and fatigue. A colonoscopy found a large, ulcerated mass in his transverse colon, the section that crosses the abdomen. Examination of tissue confirmed colon adenocarcinoma, a cancer arising from glandular cells in the bowel lining.

His family history gave doctors another reason for concern. His father, paternal aunt, an older relative and a cousin had also been diagnosed with similar disease. Gene sequencing then identified an MLH1 mutation, leading to a diagnosis of Lynch syndrome.

Associate Professor Pham Cam Phuong, director of the institute, explains that Lynch syndrome involves inherited changes affecting genes responsible for repairing errors when DNA is copied. When that repair process fails, errors can accumulate and increase the chance of cancer developing.

For this family, the next step extended beyond the patient's treatment. Doctors counselled him and his relatives about inherited risk, including the need for his older brother to receive an assessment. The brother's genetic test result and the patient's subsequent treatment outcome were not disclosed.

Lynch syndrome and FAP require different plans

Lynch syndrome accounts for about 3% of colorectal cancer cases. It is associated with harmful changes in MLH1, MSH2, MSH6 and PMS2, or changes involving EPCAM that can disrupt the repair system. These genes normally help cells correct mistakes in their DNA, much like a proofreading system.

Some people with Lynch syndrome face lifetime colorectal cancer risks reaching 50% to 80%, depending on the affected gene; risks vary substantially between genes and individuals. Cancer often develops before age 50. The syndrome also increases the risk of cancers of the endometrium, the lining of the uterus, as well as the ovaries, stomach and urinary tract.

Familial adenomatous polyposis, or FAP, accounts for fewer than 1% of colorectal cancer cases and is usually associated with an APC gene mutation. People with classic FAP can develop hundreds or thousands of polyps from their teenage years. Polyps are growths on the bowel lining, some of which can become cancerous.

Without intervention, classic FAP carries a near certainty of colorectal cancer, often before age 40. Its surveillance therefore starts much earlier than routine screening for the general population. Lynch syndrome and FAP both require specialist care, but their different patterns call for different monitoring and treatment decisions.

Vietnamese studies reveal different genetic patterns

The 2023 hereditary cancer study, published in Familial Cancer, found hereditary colorectal cancer syndrome mutations in 3% of the genetic test results examined. PMS2 was the most frequently affected gene among identified cases, while MLH1 was the least frequent.

An earlier Vietnamese genetic cohort study, published on January 5, 2022, examined 1,165 people tested during 2020. Fifteen participants, or 1.3%, carried harmful variants in genes associated with hereditary colorectal cancer syndromes. MSH6 was the most frequent Lynch associated finding, with a carrier frequency of 0.4%.

That cohort reported carrier frequencies of 0.8% for Lynch associated genes, 0.3% for APC and 0.3% for MUTYH. Interpreting MUTYH results requires attention to whether one or both gene copies are affected, because MUTYH associated polyposis usually involves harmful variants in both copies.

The 2022 study's participants were drawn from genetic testing programmes, 90.9% were women, and 34.6% had a personal or family history of cancer. The authors explain that the sample included a higher proportion of people at increased hereditary risk than the Vietnamese population. Its 3.2% carrier estimate across all hereditary cancer genes therefore needs that context.

The research and national estimates developed across several years:

• January to December 2020: The earlier cohort enrolled 1,165 Vietnamese participants for genetic testing.
• January 5, 2022: The cohort's genetic findings were published.
• July 30, 2023: The Familial Cancer study reported 49 hereditary colorectal cancer syndrome cases among 1,632 test results.
• 2024: The reference year for the latest national and global cancer burden estimates.
• July 8, 2026: The global analysis of the 2024 estimates was published online.

Why a positive test may not lead to screening

The 2023 study found that psychological concerns were the leading reported barrier to genetic testing among relatives. Reasons included fear, lack of interest and a belief that testing was unnecessary. The researchers called for better counselling before and after testing, more follow-up and policy changes concerning direct contact with relatives.

Cascade testing means offering testing to blood relatives after a harmful inherited variant is found in one family member. Instead of starting with an unknown genetic cause, clinicians can check relatives for the specific variant already identified in the family.

The study described progress in promoting this process through financial and technical support. Its participation figures also point to a gap between identifying risk and acting on it: fewer than half of cases underwent further screening, and fewer than half of families took up testing.

Access remains another issue. The 2022 study described limited availability of hereditary cancer testing in Vietnam and elsewhere in Asia because of cost and shortages of trained laboratories and healthcare professionals. Families need understandable counselling and a practical surveillance plan alongside the laboratory result.

Who should discuss earlier checks?

A parent, sibling or child with colorectal cancer can roughly double a person's risk. Risk may be three to four times higher when a close relative was diagnosed before age 50 or when several close relatives are affected. Around 20% to 30% of cases show a family pattern, including families without an identified inherited mutation.

Pham Cam Phuong recommends prioritising genetic assessment for people with a close relative carrying a Lynch associated mutation, several relatives on the same side of the family with related cancers, or cancer occurring at unusually young ages. A person who develops more than one primary cancer, meaning separate cancers that began independently, may also need assessment.

For many people with Lynch syndrome, colonoscopy begins around ages 20 to 25 and is repeated every one to two years, with timing adjusted to the gene and family history. Monitoring for classic FAP often starts around ages 10 to 12. A colonoscopy uses a flexible camera to inspect the bowel and allows doctors to remove many polyps during the examination.

People aged 45 or older should discuss routine screening, while those with inherited risk may need care much sooner. Other groups needing individual assessment include people with previous colorectal cancer or adenomatous polyps, longstanding ulcerative colitis or Crohn's disease, and previous radiation treatment to the abdomen or pelvis. Inflammatory bowel disease becomes a particular concern after roughly eight to ten years.

For people already diagnosed with colorectal cancer, tumour testing for deficient mismatch repair, known as dMMR, or high microsatellite instability, known as MSI-H, can guide further assessment. These findings indicate problems in DNA repair. They can prompt testing for Lynch syndrome and help identify patients who may benefit from immunotherapy, treatment that helps the immune system attack cancer.

Earlier detection depends on participation

Dr Nguyen Duy Anh, deputy director of the Oncology, Radiotherapy and Nuclear Medicine Center at Phuong Dong General Hospital, identifies three connected problems: changing cancer patterns, urban diets and lifestyles, and late detection. He describes many patients arriving after symptoms develop, including people already at stages III or IV.

Vietnam has no organised nationwide colorectal cancer screening programme. Fear of pain, embarrassment and the belief that healthy people do not need checks can delay participation. Blood in the stool may be attributed to haemorrhoids, while changes in bowel habits may be treated as ordinary bowel trouble, postponing medical assessment.

Nguyen Duy Anh says endoscopy assisted by artificial intelligence can improve detection of adenomas, polyps that can develop into cancer. Reaching people eligible for screening remains central: better equipment benefits patients when they attend an examination.

Ageing, improved diagnosis and changing exposures all contribute to the recorded burden. Smoking, heavy alcohol consumption, excess weight, type 2 diabetes, inactivity, and diets high in red or processed meat and low in fibre deserve attention alongside family history. For patients and relatives, the practical response is a risk assessment that connects prevention, screening and genetic advice rather than treating them as separate tasks.

Key Points

• Vietnam had an estimated 22,584 new colorectal cancer cases and 10,990 deaths in 2024.
• Asia accounted for more than half of global colorectal cancer diagnoses and deaths.
• A 2023 Vietnamese study identified hereditary colorectal cancer syndrome mutations in 49 of 1,632 genetic test results.
• Only 44% of identified cases underwent further screening, while 48% of their families took up genetic testing.
• Lynch syndrome and FAP can require surveillance decades before routine screening ages.
• Early diagnoses and clusters of related cancers in a family should prompt discussion of genetic counselling.
• Tumour testing can help guide both hereditary risk assessment and treatment choices.