Bowel cancer, also called colorectal cancer, is the most common cancer in Singapore and one of the leading causes of cancer death here. It’s also one of the more treatable cancers when caught early, which is why understanding its causes, symptoms, and how it’s diagnosed matters. This guide covers what bowel cancer is, what increases your risk, the symptoms to watch for, how doctors diagnose and stage it, and the treatment options typically used.
Bowel cancer occurs when cells in the lining of the large intestine (colon or rectum) grow abnormally and uncontrollably. It can develop anywhere along the large intestine, including the rectum. Most bowel cancers start as a small, usually non-cancerous growth on the bowel lining called a polyp. Not all polyps turn into cancer, and this transformation, when it happens, tends to occur gradually — often over several years. If left untreated, cancerous cells can spread into deeper layers of the bowel wall, nearby lymph nodes, and eventually other parts of the body.
The exact cause of bowel cancer in any individual case isn’t always clear, but several factors are known to increase risk.
Risk rises with age – the majority of cases are diagnosed in people over 50, and incidence continues to climb in older age groups. A family history of bowel cancer, especially in a close relative (parent or sibling) diagnosed before age 50, also raises personal risk.
A small proportion of bowel cancers are linked to inherited conditions:
People with long-standing inflammatory bowel disease – particularly Crohn’s disease or ulcerative colitis present for many years – have a higher risk and are typically offered more frequent colonoscopy monitoring as part of their ongoing care.
A diet high in red and processed meat, low fibre intake, regular smoking, higher alcohol consumption, physical inactivity, and obesity have all been associated with increased risk in research studies. These are modifiable factors – meaning lifestyle changes may help lower risk, though they don’t eliminate it entirely.
In its early stages, bowel cancer often causes no symptoms at all – which is a key reason age-based screening is recommended rather than waiting for symptoms to appear. When symptoms do occur, they can include:
These symptoms are common to many conditions that are far less serious than cancer, such as haemorrhoids or infections – so having one of them doesn’t mean you have bowel cancer. It does mean it’s worth getting checked rather than waiting it out, particularly if symptoms persist beyond a few weeks.
Diagnosis usually starts one of two ways: through routine screening in someone without symptoms, or through investigation after a doctor visit about symptoms.
Once cancer is confirmed by biopsy, further imaging helps determine how far it has spread – information that guides treatment planning:
Not everyone needs every scan – the doctor decides based on what’s found during colonoscopy and biopsy.
Because bowel cancer often develops silently over years from a polyp before causing symptoms, national screening is designed to catch it early – including at a pre-cancerous polyp stage, when it can often simply be removed during colonoscopy.
Under the Healthier SG Screening programme, Singapore Citizens aged 50 and above who haven’t had a FIT test within the past year are eligible, with visits costing as little as $0–$5 depending on enrolment status. People with a family history or other risk factors may be advised to start screening earlier and more frequently – this is worth discussing directly with a doctor.
Treatment depends on the type, location, and stage of the cancer, and is typically planned by a multidisciplinary care team. Common approaches include:
Because treatment plans are highly individual, this is best discussed directly with the treating specialist, who can explain what applies to a specific diagnosis and stage.
While not all bowel cancer can be prevented, several steps may help lower risk:
See a doctor if you notice:
Even without symptoms, if you’re a Singapore Citizen aged 50 or above, it’s worth checking your eligibility for subsidised colorectal screening under Healthier SG rather than waiting for symptoms to appear.
When diagnosed at an early stage, bowel cancer is often treatable, and outcomes tend to be more favourable the earlier it’s found – which is a key reason screening and early symptom review matter. Outlook varies by individual and stage, and a treating doctor can give a more specific picture for a particular diagnosis.
No. Blood tests such as CEA can support the picture but aren’t accurate enough alone to confirm or rule out bowel cancer. A biopsy taken during colonoscopy is needed for a definitive diagnosis.
No. A positive FIT means blood was detected in the stool, which has several possible causes – including polyps, haemorrhoids, or cancer. A colonoscopy is needed to find the actual cause.
Under Healthier SG, average-risk Singapore Citizens are generally eligible for FIT screening from age 50. Those with a family history or other risk factors may need to start earlier and more frequently – a doctor can advise on the appropriate age and interval.
Yes. Bowel cancer often develops without symptoms in its earlier, more treatable stages, which is exactly why age-based screening rather than waiting for symptoms is recommended.
No. Most polyps are non-cancerous growths. Only some develop into cancer over time, which is why they’re typically removed and checked when found during colonoscopy, rather than left in place.
Bowel cancer develops gradually in many cases, often from a polyp, and screening is one of the most effective tools for catching it before it causes symptoms. If you have symptoms that concern you, want to understand your risk factors, or want to check your eligibility for subsidised colorectal screening, you can consult a doctor through the MaNaDr App to discuss your next steps.
