Review & Public Health Guidance
Cancer Screening
Key Takeaways
- Fecal occult blood test (FOBT) screening has been proven to reduce colorectal cancer mortality by 15–33% in large randomised controlled trials.
- FOBT works by detecting tiny amounts of blood in the stool that are invisible to the naked eye — blood that may indicate polyps, early cancers, or other conditions in the colon or rectum.
- The newer immunochemical FOBT (FIT) is more accurate than the older guaiac-based test, does not require dietary restrictions, and needs only one stool sample.
- Despite the proven benefits, colorectal cancer screening rates in Malaysia remain low, with most cases diagnosed at advanced stages when treatment is less effective.
Colorectal Cancer in Malaysia: A Growing Concern
Colorectal cancer — cancer of the colon or rectum — is the most common cancer among Malaysian men and the second most common cancer among Malaysian women, after breast cancer. Data from the Malaysian National Cancer Registry have shown a steady increase in colorectal cancer incidence over recent decades, a trend attributed to changes in diet (increased consumption of processed food and red meat, decreased fibre intake), rising obesity rates, sedentary lifestyles, and an ageing population.
What makes colorectal cancer particularly tragic is that it is one of the most preventable and treatable cancers — if caught early. Colorectal cancer typically develops slowly, over a period of 10 to 15 years, from precancerous growths called polyps that form on the inner lining of the colon or rectum. During this long precancerous phase, screening can detect and remove polyps before they become cancerous. Even when cancer has already developed, detection at an early stage (stage I or II) is associated with five-year survival rates exceeding 90%.
Yet in Malaysia, the majority of colorectal cancer cases are diagnosed at late stages (stage III or IV), when the cancer has already spread to lymph nodes or distant organs and five-year survival drops to below 15%. This pattern — late diagnosis leading to poor outcomes — is primarily a failure of screening. Most Malaysians who develop colorectal cancer have never been screened.
What Is the Fecal Occult Blood Test?
The fecal occult blood test (FOBT) is a simple, non-invasive screening test that detects tiny amounts of blood in the stool — “occult” meaning hidden, because the blood is present in quantities too small to be seen with the naked eye. The premise is straightforward: colorectal polyps and cancers often bleed small amounts as stool passes over them, and detecting this blood can identify individuals who need further investigation with colonoscopy.
There are two main types of FOBT, and understanding the difference is important because they differ significantly in accuracy and convenience.
| Feature | Guaiac FOBT (gFOBT) | Immunochemical FOBT (FIT) |
|---|---|---|
| How it works | Detects the peroxidase activity of haemoglobin using a chemical reaction | Uses antibodies specific to human haemoglobin |
| Dietary restrictions | Yes — must avoid red meat, certain vegetables, and vitamin C for 3 days before test | None — specific to human blood only |
| Samples required | Multiple samples from 3 consecutive bowel movements | Usually 1 sample |
| Sensitivity for cancer | ~50–60% | ~75–80% |
| False positives | Higher — can react to animal blood in food | Lower — only detects human blood |
| Cost | Very low | Low to moderate |
| Current recommendation | Being phased out in favour of FIT | Preferred test in most guidelines |
The immunochemical FOBT (FIT) is now the preferred screening method in most international guidelines because of its superior accuracy, ease of use, and the absence of dietary restrictions that often led to poor compliance with the older guaiac test.
The Evidence: Does Screening Actually Save Lives?
The evidence that FOBT screening reduces colorectal cancer deaths is strong. Four large randomised controlled trials — conducted in the United States (Minnesota), the United Kingdom (Nottingham), Denmark (Funen), and Sweden (Gothenburg) — have collectively demonstrated that regular FOBT screening reduces colorectal cancer mortality by approximately 15 to 33%, depending on the frequency of screening and the length of follow-up.
The Minnesota trial, which followed participants for over 18 years, showed that annual FOBT screening reduced colorectal cancer mortality by 33%. Even biennial (every two years) screening achieved a significant reduction of approximately 21%. These are among the most robust findings in cancer screening research.
It is important to understand what FOBT screening achieves and what it does not. FOBT is not a diagnostic test — a positive result does not mean a person has cancer. It means that blood was detected in the stool, and further investigation (usually colonoscopy) is needed to determine the cause. Blood in the stool can result from many conditions other than cancer, including haemorrhoids, inflammatory bowel disease, and benign polyps. Approximately 2–10% of people who take the FOBT will have a positive result, and of those, only a small proportion will turn out to have cancer. But for those who do, early detection can be life-saving.
Who Should Be Screened?
International guidelines, including those from the World Health Organization and the Asia Pacific Consensus on Colorectal Cancer, generally recommend that colorectal cancer screening should begin at age 50 for individuals at average risk and continue until age 75. However, some recent guidelines have suggested starting screening at age 45, reflecting the increasing incidence of colorectal cancer in younger adults observed in many countries.
Individuals at higher-than-average risk should discuss screening with their doctor, as they may need to start earlier or be screened with colonoscopy rather than FOBT. Higher risk factors include a first-degree relative (parent, sibling, or child) with colorectal cancer, a personal history of colorectal polyps, inflammatory bowel disease (Crohn’s disease or ulcerative colitis), and certain hereditary conditions such as Lynch syndrome or familial adenomatous polyposis.
Why Screening Rates Remain Low in Malaysia
Despite the clear evidence that screening saves lives, colorectal cancer screening uptake in Malaysia remains disappointingly low. Unlike breast cancer screening (mammography) and cervical cancer screening (Pap smear), which have established national programmes and relatively higher awareness, colorectal cancer screening has received less public health attention and investment.
Several barriers contribute to low screening rates. Awareness is a primary issue — many Malaysians are simply unaware that colorectal cancer screening exists or that it is recommended for them. Cultural factors play a role — discussing bowel habits and providing stool samples can be embarrassing, and some people avoid the topic entirely. The “I feel fine” phenomenon is powerful — because colorectal cancer in its early stages and precancerous polyps typically cause no symptoms, people who feel healthy see no reason to be screened. Fear of results, cost concerns (for those without insurance or outside the public system), and limited access to screening services, particularly in rural areas, are additional barriers.
What You Should Do
If you are aged 50 or older (or 45 or older if you follow the latest recommendations) and have never been screened for colorectal cancer, talk to your doctor about FOBT/FIT screening. The test is simple, can be done at home with a kit provided by your clinic, and requires only a small stool sample. If the result is positive, your doctor will refer you for colonoscopy — an important follow-up step that should not be avoided. If the result is negative, repeat the test every one to two years as recommended.
If you have a family history of colorectal cancer, speak to your doctor regardless of your age — you may need earlier or more frequent screening.
Implications for Malaysian Public Health
Malaysia would benefit from a structured national colorectal cancer screening programme, similar to the existing programmes for breast and cervical cancer. Such a programme could use FIT as the primary screening tool, distributed through Klinik Kesihatan and community pharmacies, with a clear referral pathway for positive results. Public awareness campaigns should normalise the conversation about bowel health and cancer screening, using culturally appropriate messaging in multiple languages. Healthcare providers at the primary care level should be trained and incentivised to recommend colorectal cancer screening as part of routine health assessments for adults aged 50 and above.