Colorectal Cancer

Colorectal cancer is the second leading cause of death in both men and women in Singapore (Singapore Cancer Registry Annual Report 2021). Screening tests such as the faecal immunochemical test (FIT) and screening colonoscopy can help prevent it.

What is Colorectal Cancer? 

Colorectal cancer is cancer of the colon (the main part of the large intestine) and the rectum (the passageway connecting the colon to the anus). 
In most people, colorectal cancers develop slowly over several years. Before cancer forms, a growth of tissue or a tumour usually begins as a non-cancerous polyp on the inner lining of the colon or rectum. A polyp is a benign or non-cancerous growth which may develop into cancer over time. Not all polyps change into cancer and this largely depends on the kind of polyp.



Risk Factors

You have a higher chance of developing colorectal cancer if you:
  • Are over 50 years of age
  • Have a family history of colon or rectum cancer
  • Have a previous history of colon polyps
  • Have a history of ulcerative colitis (ulcers in the lining of the large intestine) or Crohn’s disease
  • Smoke or have a diet high in fats and low in fruits and vegetables
If you think you may be at risk, you should discuss this with your doctor.

Colorectal Cancer Symptoms 

In the early stages, people with colorectal cancer may not experience any symptoms.
In the later stages, common symptoms include:
  • A change in bowel habits, including diarrhoea or constipation
  • Presence of blood in stools
  • Persistent abdominal discomfort such as cramps, gas or pain

Related: Signs and Symptoms of Colorectal Cancer

Colorectal Cancer Screening 


For average-risk individuals, screening for colorectal cancer should begin at age 50 years. FIT is one of the recommended screening tests and should be performed annually. Average-risk individuals refer to asymptomatic individuals and individuals who do not have a family history of colorectal cancer, as well as those with family history confined to non-first degree relatives or relatives older than 60 years old.
You can undergo colorectal cancer screening (using FIT) through HPB's Screen for Life programme. You will be given two FIT kits because two stool samples should be collected over two days for a more accurate result.
Screening using FIT should be done once a year. However, if you develop any colorectal cancer signs or symptoms even after a normal FIT result, please see your doctor immediately.

For individuals at increased risk or high risk, screening by colonoscopy is also indicated. Please refer to the table below

Risk Group
Onset (Age) Frequency of colonoscopy screening
i) Average Risk
1. Asymptomatic or family history limited to non-first degree relatives
50 years
Every 5 to 10 years
ii) Increased Risk
1. Colorectal cancer in first degree relative (parent, sibling) age 60 yrs or younger or two or more first degree relatives
10 yrs prior to youngest case in the family or age 40 yrs, whichever is earlier
Every 5 years
2. Colorectal cancer in first degree relative over the age of 60 yrs
50 years
Every 5 to 10 years
3. Personal history of colorectal polyps
1 to 3 yrs after polypectomy in the presence of high risk features (>1cm, multiple, villous architecture); otherwise, 3 to 5 yrs after polypectomy for low risk polyps
4. Personal history of colorectal malignancy
One year after resection
Every 1 to 3 years
5. Personal history of ovarian or endometrial cancer
After resection
iii) High Risk

1. Family history of familial adenomatous polyposis^
10 to 12 years (from puberty)
2. Family history of hereditary non-polyposis colorectal cancer (Lynch Syndrome )^
20 to 25 yrs 
Every 1 to 2 years
3. Inflammatory Bowel Disease 

a. Left-sided colitis
From 15th yr of diagnosis
Every 1 to 2 years
b. Pan-colitis
From 8th yr of diagnosis
Every 1 to 2 years

*Flexible sigmoidoscopy from age 10 to 12 years (puberty) until adenomas are identified, upon which screening is switched to colonoscopy 

^Refer to Annex E for guidelines to refer suspected individuals for cancer genetic risk assessment.

The above colorectal screening information is taken from the Report of the Screening Test Review Committee.


Colonoscopy is one of the recommended screening tests for the average risk asymptomatic population, from age 50 years. For screening the general population at average risk, colonoscopy should be performed at an interval of no more than 5 to 10 years.

The screening colonoscopy:
  • Uses a flexible tube (colonoscope) to look at the inner lining of the large intestine (colon and rectum)
  • Takes about 20 to 30 minutes to complete
  • Has to be done in a hospital by a doctor trained in conducting colonoscopies



Discuss with your doctor which screening test is best for you.

For more information about your recommended screening for colorectal cancer, visit the Screen for Life page.


Colorectal Cancer Treatment 

The three main treatment options for colorectal cancer are surgery, chemotherapy and radiation. These options may be used alone or in a combination.
  • Colorectal surgery: this involves removal of the part of the colon that contains the cancer cells.
  • Chemotherapy: chemotherapy can be used to destroy cancer cells after surgery, to control tumour growth or to relieve symptoms of colorectal cancer.
  • Radiation therapy: radiation therapy uses X-rays to kill any cancer cells that might remain after surgery, to shrink large tumours before an operation so that they can be removed more easily, or to relieve symptoms of colorectal cancer. Side effects of radiation therapy may include:  
    • Diarrhoea
    • Rectal bleeding
    • Fatigue

Colorectal Cancer Prevention 

A healthy lifestyle can help prevent colorectal cancer and many other diseases. Take steps to reduce your risk of colorectal cancer by: 
  • Eating plenty of fruits, vegetables and whole grains which contain fibre and antioxidants
  • Limiting fat especially saturated fat from animal sources such as red meat, milk, cheese and ice cream (plant-based "vegetable oil" can also be high in saturated fat)
  • Limiting alcohol intake
  • Quitting smoking
  • Staying physically active and maintaining a healthy body weight

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