Can Colorectal Cancer Be Prevented? What You Should Know

Colorectal cancer usually begins with abnormal changes in the cells lining the colon or rectum. These changes may lead to precancerous polyps, which can accumulate further mutations and eventually become invasive cancer. Understanding this progression also shows why screening matters, as certain polyps can be identified and removed before cancer develops.

Colorectal cancer affects the colon or rectum, which are parts of the large intestine. It cannot always be prevented, but some cases may be avoided when precancerous growths, called polyps, are found and removed early.

Screening also gives doctors a chance to detect colorectal cancer before it causes symptoms. At the National Cancer Centre Singapore (NCCS), we help patients understand their diagnosis, treatment options and individual risk factors for colorectal cancer.

Key Takeaways

• Colorectal cancer cannot always be prevented, but screening can find certain polyps before they become cancerous.
• Polyps are common and are not automatically cancerous, although some types can develop into cancer over time.
• Regular physical activity, a healthy weight, avoiding smoking and limiting alcohol can support overall bowel health and lower cancer risk.
• Blood in the stool, ongoing changes in bowel habits, unexplained weight loss and persistent abdominal discomfort should be assessed by a doctor.
• People with a strong family history, previous polyps or inflammatory bowel disease may need earlier or more frequent screening.

How Does Colorectal Cancer Start?

Colorectal cancer usually starts in the inner lining of the colon or rectum. Cells in this lining regularly grow, divide and are replaced as part of the body’s normal process.

Sometimes, a small group of cells begins to grow in an unusual way. This can form a polyp, which is a growth on the inner wall of the bowel. Polyps can vary in size and shape. Some remain harmless, while others may slowly develop into cancer over several years.

Not every colorectal cancer begins from a visible polyp, and not every polyp turns into cancer. Still, finding and removing certain polyps is one of the most important ways to reduce the risk of colorectal cancer.

Can Polyps Turn Into Colorectal Cancer?

Over time, some polyps may change and become cancerous.

Doctors usually remove a polyp during a colonoscopy and send it to a laboratory for examination. The results help determine the type of polyp and whether it has features linked to a higher chance of future cancer development.

A doctor may consider:

• The type and size of the polyp
• How many polyps were found
• Whether abnormal cells were present
• Whether the polyp was fully removed
• Your personal and family medical history

The follow-up plan depends on these findings. Someone with a small, low-risk polyp may not need another colonoscopy for several years, while another person may need closer monitoring.

From a Polyp to Cancer: The Basic Process

This process often takes years. That is why screening can be valuable even when a person feels completely well.

Who May Have a Higher Risk of Colorectal Cancer?

Colorectal cancer can affect people without a known family history. However, some factors can increase a person’s risk.

Age

The risk of colorectal cancer rises with age. This is why routine screening is recommended for adults from a certain age onward, even when they have no symptoms.

Family history

Having a parent, sibling or child with colorectal cancer can increase the risk, especially if that relative was diagnosed at a younger age. A family history of multiple polyps may also be relevant.

Tell your doctor about relatives who have had colorectal cancer, bowel polyps, uterine cancer or certain other cancers. This information can help determine if you need earlier screening or genetic assessment.

Previous polyps

A person who has had certain types of polyps removed may need follow-up colonoscopies. The aim is to check for new polyps and remove them before they cause problems.

Inflammatory bowel disease

Long-term inflammatory bowel conditions, such as ulcerative colitis or Crohn’s disease affecting the colon, may increase colorectal cancer risk. People with these conditions are usually given an individual surveillance plan by their medical team.

Lifestyle and overall health

Lifestyle factors do not explain every case of colorectal cancer, but some habits are linked to a higher risk. These include smoking, heavy alcohol intake, low physical activity, obesity and a diet high in processed meat.

What Can You Do to Lower Your Risk?

There is no guaranteed way to prevent every case of colorectal cancer. Age, inherited genes and family history are not within a person’s control. However, practical steps can support better bowel and overall health.

Attend recommended screening

Screening is one of the most effective actions a person can take because it may identify cancer early or find polyps before cancer develops.

In Singapore, current guidance recommends that people aged 50 and above complete a Faecal Immunochemical Test (FIT) every year or have a colonoscopy once every five to ten years. The suitable option depends on a person’s health profile and risk factors. HealthHub’s evidence-based screening recommendations provide further guidance on screening tests for the general population.

People with symptoms or a higher risk should not wait for routine screening. They may need an earlier medical assessment.

Stay physically active

Regular activity supports healthy body weight, bowel movement and metabolic health. Brisk walking, swimming, cycling or other activities that fit your fitness level can all contribute.

The goal is to build a routine that feels sustainable. Starting gradually is still beneficial if exercise has not been part of your usual schedule.

Maintain a healthy weight

Excess body weight is associated with a higher risk of several cancers, including colorectal cancer. Weight management does not need to involve extreme diets. Small, consistent changes in eating habits and activity can make a meaningful difference over time.

Eat a balanced diet

A balanced eating pattern can include vegetables, fruit, wholegrains, pulses, fish and other sources of lean protein. Try to limit processed meats, such as bacon, sausages and ham, and keep red meat portions moderate.

No individual food or supplement can guarantee protection against colorectal cancer. A healthy overall eating pattern is more useful than relying on a single product or “detox” programme.

Avoid smoking and limit alcohol

Smoking can increase the risk of colorectal cancer and other serious health conditions.

Alcohol intake should also be kept within recommended limits. People who drink regularly may wish to speak with a healthcare professional about reducing their intake.

What Symptoms Should Not Be Ignored?

Early colorectal cancer and polyps may not cause noticeable symptoms. This is why screening matters.

However, you should see a doctor if you notice:

• Blood in the stool or bleeding from the rectum
• A persistent change in bowel habits, such as diarrhoea, constipation or narrower stools
• Ongoing abdominal pain, bloating or discomfort
• A feeling that the bowel does not empty fully
• Unexplained weight loss
• Unusual tiredness or shortness of breath caused by low iron levels
• A lump in the abdomen or rectum

These symptoms can be caused by conditions other than cancer, including haemorrhoids, infections and irritable bowel syndrome. Nonetheless, seek medical advice if you experience these symptoms, especially if they persist or worsen.

Do not rely on a screening test alone if you have symptoms. Screening is designed for people who do not have warning signs.

What Happens During Colorectal Cancer Screening?

Faecal Immunochemical Test

The Faecal Immunochemical Test, or FIT, is a simple stool test that looks for tiny traces of blood that may not be visible to the eye.

A positive FIT result does not mean that a person has colorectal cancer. Blood in the stool can have several causes. A positive result means that further assessment, usually a colonoscopy, is needed to find the source of the blood.

Colonoscopy

A colonoscopy allows a doctor to examine the inside of the colon and rectum using a flexible tube with a small camera. It is usually performed after bowel preparation, which clears the bowel so the lining can be seen clearly.

During the procedure, the doctor can often remove small polyps straight away. These polyps are then examined in a laboratory. This is why colonoscopy can help with both early detection and prevention.

What If You Have a Family History?

A family history does not mean you will definitely develop colorectal cancer. It does mean that your doctor may recommend screening earlier or more often than routine guidance suggests.

It can be helpful to find out:

• Which relative had colorectal cancer or polyps
• The relative’s age at diagnosis
• Whether other relatives have had similar cancers
• Whether anyone in the family has had genetic testing

Share this information with your doctor at your medical appointment if possible. Your doctor can decide if you need referral for genetic counselling or a personalised screening plan.

Earlier Action Can Make a Difference

Colorectal cancer cannot always be prevented, but some cases may be avoided when pre-cancerous polyps are found and removed. Screening, healthy lifestyle habits and attention to symptoms can all support earlier action.

If you have bowel symptoms or are concerned about your family history, speak with a doctor for advice. If colorectal cancer is diagnosed, NCCS provides personalised colorectal cancer treatment based on the cancer stage, location and each patient’s individual needs.

Frequently Asked Questions

1. Can a FIT test detect polyps?
   A FIT test looks for small traces of blood in the stool. Some polyps may bleed, but not all do. A negative FIT result does not rule out every polyp, which is why regular screening remains important.
   
   
2. Does a positive FIT result mean I have cancer?
   A positive FIT result does not confirm cancer. Bleeding may also come from haemorrhoids, polyps or other bowel conditions. Your doctor will usually recommend a colonoscopy to identify the cause.
   
   
3. Are all bowel polyps cancerous?
   No. Most bowel polyps are not cancerous. Some types can develop into cancer over time, which is why doctors often remove them during colonoscopy.
   
   
4. Can younger adults develop colorectal cancer?
   Colorectal cancer is more common in older adults, but younger people can develop it too. Persistent bowel symptoms, rectal bleeding or a strong family history should be discussed with a doctor, regardless of age.
   
   
5. How often should I have colorectal cancer screening?
   For people at average risk in Singapore, screening guidance recommends a FIT every year or a colonoscopy once every five to ten years from age 50. Your doctor may suggest a different schedule if you have symptoms, previous polyps, inflammatory bowel disease or a significant family history.