Colorectal Cancer – Symptoms, Treatments | SingHealth
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Colorectal Cancer

Colorectal Cancer - What it is

The large intestine or colon, is the final part of the digestive tract. It is responsible for absorbing water from the food that we eat and turning indigestible food into waste.

Colorectal cancer is a type of cancer that starts in the colon or rectum. Colon cancer and rectal cancer are often grouped together and known as colorectal cancer, due to their common features. Nearly all colorectal cancers begin as polyps, which are benign growths on the inner lining of the colon or rectum. Over time, some of these polyps can change and become cancerous. Polyps may be small and generally do not cause any symptoms.

Some colorectal cancers arise from the innermost lining of the colon or rectum without the development of polyps. Cancer cells can grow deep into the wall of the colon or rectum and may extend into the fatty tissue that surrounds the colon and rectum. Colorectal cancer can also spread to nearby lymph nodes. In some cases, cancer cells spread through blood vessels to other parts of the body such as the liver.

Colorectal cancer is the most common cancer in Singapore, affecting approximately 45 out of every 100,000 people here. For men, it is the second most common type of cancer and for women it comes second after breast cancer. During a period of five years, between 2017-2021, 12,239 cases of colorectal cancer were diagnosed in Singapore.

Colorectal cancer is most commonly diagnosed in people aged 50 years and above. However, colorectal incidence is also rising amongst younger individuals under the age of 50.

Younger individuals who are diagnosed with colorectal cancer may have hereditary conditions including familial adenomatous polyposis (FAP)or hereditary non-polyposis colorectal cancer. There may also be sporadic (non-hereditary) cases of young colorectal cancer.

Regular screening tests are recommended to help prevent colon cancer by identifying and removing polyps before they turn into cancer.

Colorectal Cancer - Symptoms

In the early stages, colorectal cancer may not cause any symptoms. In later stages, symptoms may include:

  • Persistent diarrhoea or constipation
  • Blood in the stools or rectal bleeding
  • Change in the consistency or calibre of stools
  • General abdominal discomfort (bloating, fullness, cramps or gas)
  • A feeling that the bowel does not completely empty after emptying the bowels
  • Constant tiredness
  • Severe appetite or weight loss

When to see a doctor

The symptoms above can be caused by a number of reasons and may not indicate the presence of cancer. However, make an appointment with your doctor if you have any signs or symptoms that worry you.

Colorectal Cancer - How to prevent?

Regular screening is the best way to detect colorectal polyps or cancer early. In Singapore, the recommended age of screening for colorectal cancer is 50 years old for individuals with no symptoms. Individuals with a family history of colorectal cancer are advised to start screening earlier.

Routine screening tests include:

  • Faecal Immunochemical Test (FIT) (yearly)
    • Blood in the stool may be an early sign of colorectal cancer. FIT is used to detect the presence of human blood in the stool. If blood is found, additional tests can confirm the source of the blood and if it is cancer.
  • Colonoscopy (every 5-10 years)      
    • During this procedure the colon and rectum are examined using a special flexible camera inserted through the anus. It allows the removal of small polyps and biopsy of any abnormal areas.

In addition to regular screening, a healthy lifestyle may help to prevent colorectal cancer. This includes:

  • Eating a diet rich in fruit, vegetables and whole grains, while limiting the consumption of fat.
  • Quitting or not starting smoking.
  • Limiting alcohol consumption.
  • Regular exercise.

Colorectal Cancer - Causes and Risk Factors

Factors that can increase the risk of colorectal cancer include:

  • Older age – Colorectal cancer is often diagnosed in people aged 50 years and above. However, younger people can also be diagnosed with the cancer.
  • History of colorectal polyps or cancer
  • Inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease.
  • Family history of colorectal cancer, familial adenomatous polyposis or hereditary non-polyposis colorectal cancer.
  • Diabetes - people with diabetes or insulin resistance are at increased risk of colon cancer.
  • A low-fibre, high fat diet
  • A sedentary lifestyle
  • Smoking
  • Heavy use of alcohol

Colorectal Cancer - Diagnosis

There are a number of different tests that can be used to detect polyps, cancer or other abnormalities in the colon and rectum.

Before some of these tests, the colon must be completely empty and the doctor may prescribe an enema or a liquid laxative. This preparation is very important in ensuring the test accuracy.

Diagnostic tests include:

  • Colonoscopy
    • Part of regular screening and diagnostic procedures, a colonoscopy examines the colon and rectum using a special flexible camera inserted through the anus. It allows the removal of small polyps and taking of tissue samples (biopsies) of any abnormal areas.
  • Digital rectal examination
      Often part of a routine physical examination, the doctor checks the lower most area of the rectum by inserting a lubricated gloved finger into the rectum and gently feeling for abnormal growths. The exam may be uncomfortable but should not be painful.
  • Double Contrast Barium Enema
    • In this procedure, the colon and rectum is filled with a white liquid, called barium, that helps x-rays show extra details, including polyps, in the large intestines better than normal x-rays.
  • Computed Tomographic Colonography (CTC)
    • A CTC or virtual colonoscopy creates a 3D image of the colon to reveal any abnormal masses. Images are taken seconds after the colon is inflated with carbon dioxide through a small rectal tube and is sensitive enough to detect more abnormal growths than other tests.
  • Flexible sigmoidoscopy
    • A narrow lighted tubular instrument called a sigmoidoscope is passed into the rectum allowing the doctor to look into the rectum and left-sided part of the colon. This also enables taking of tissue samples (biopsies) of any abnormal areas.

If diagnosed with colon cancer, the doctor may recommend further tests to determine the extent or stage of cancer. These are usually imaging tests for the abdominal, pelvic and chest areas.

In some cases, the extent of the cancer will only be known after surgery.

Colorectal Cancer - Treatments

Treatment for colorectal cancer depends on the location, size, stage and grade of the cancer.

An individual with colorectal cancer should be assessed by a multi-disciplinary team of specialists to determine which modality of treatment is best suited for them. Colorectal cancer treatment requires the involvement of different specialists – surgeons, interventional radiologists, nuclear medicine physicians, medical oncologists, radiation oncologists and palliative medicine specialists. Such multi-disciplinary care is available at SingHealth healthcare institutions.

Types of treatment


Depending on the stage of cancer, there are different approaches that the surgeon may use during surgery.

In very early stages colorectal cancer, the surgeon may only remove the cancerous growth or a part of the inner lining of the colon. In more advanced stages, the surgeon may remove the section of the colon or rectum that is diseased. Nearby lymph glands will also be removed to ensure adequate removal of all cancer cells. Minimally invasive surgery or laparoscopic surgery may be performed, where the surgeon performs the operation through several small incisions in the abdominal wall This method has been shown to minimise pain after surgery and accelerate recovery, but is not suitable for all cases of colorectal cancer.

During colorectal cancer surgery, an artificial opening for the colon called a stoma may be required. This opening allows waste to be removed from the body when the normal opening cannot be used or has to be removed. A stoma may be temporary or permanent. Specialist nurses are available to help patients or their caregivers with stoma maintenance and care.

Sometimes, chemotherapy or radiotherapy may be used before or after surgery.

Increasingly, some patients with stage 4 cancer with limited spread to the liver, lung and/or the peritoneum may be suitable for surgical treatments that can provide long term disease control or even cure. Our colorectal surgeons and oncologists work closely with the liver, lung and peritoneal surgeons to coordinate surgical treatments in patients with limited spread to the other organs for which curative intent surgery may still be possible.

Chemotherapy and/or targeted therapy

Chemotherapy is the use of anti-cancer drugs to destroy cancer cells. The type of chemotherapy, how it is administered and the number of courses required, depends on the type of cancer and how well the patient is responding to the drugs. Molecular profiling of the tumour is often performed to characterise each patient’s cancer and assist in selecting the medications that a patient is more likely to respond to. We now have more systemic treatment options including targeted therapy and immunotherapy, which will be explained in more details below.

In patients with stage 2 and stage 3 cancer, chemotherapy (oxaliplatin, fluoropyrimidines) may be administered after surgery for up to 3 - 6 months, to reduce the risk of recurrence and therefore increase chances of long term survival. Patients will be followed up for 5 years with regular physical examination, blood tests and interval radiological imaging, plus colonoscopy as indicated.

In stage 4 disease where the cancer has spread to other organs, chemotherapy and/or targeted therapy is given to control the cancer in order to shrink the tumour, and to control the spread of cancer cells. Some treatments include chemotherapy (oxaliplatin, irinotecan and fluoropyrimidines), anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (panitumumab, cetuximab), anti-vascular endothelial growth factor (VEGF) monoclonal antibodies (bevacizumab, ramucirumab) and oral therapies such as encorafenib, regorafenib and TAS-102. On top of systemic therapy, some patients with oligometastatic disease (stage IV cancer with limited sites of spread) may also be amenable to further surgical resections and/or locoregional therapies. Newer treatments and clinical trials may be available for some patients and these can be discussed with your medical oncologists.

Some side effects may be experienced with chemotherapy (mouth sores, rashes, numbness, loss of appetite, nausea/vomiting, diarrhoea, low blood counts, infections, allergic responses and rarely organ dysfunction) but your condition will be monitored closely by your oncologists and usually the treatments are fairly well tolerated. We also have a strong support from palliative care services, medical social services and oncology specialist nurses/pharmacists.

Radiation therapy

Radiation or radiotherapy uses high-energy X-rays to kill cancer cells. The aim of radiotherapy is to destroy more cancer cells and spare as many normal cells as possible. Radiation therapy is sometimes used after surgery for colorectal cancer to destroy any remaining cancer cells and prevent the cancer from recurring. It may also be used to reduce the size of the rectal cancer before surgery.

In some cases, when surgery is not an option, radiation therapy is used to control the growth of tumours which are causing pain or bleeding.


Immunotherapy is a treatment that uses the patient’s own immune system (white blood cells) to fight cancer. It is given intravenously and usually used in selected cases of patients with microsatellite instability high (MSI-H) colorectal cancer, which is usually linked to a hereditary type of colorectal cancer syndrome called Lynch Syndrome. MSI-H colorectal cancers can also occur in patients without family history.

Supportive (palliative) care

Palliative care is specialised medical care that provides relief from pain and symptoms of serious illness so that a person with cancer feels better and has a better quality of life. The palliative care team of doctors, nurses and other healthcare professionals provide an additional layer of support that complements ongoing care.

Colorectal Cancer - Preparing for surgery

Your surgeon will perform a comprehensive medical work-up including blood tests and scans to see if you are suitable for surgery and advise you on the risks involved. This treatment recommendation is often based on consensus by a group of different specialists' opinions (tumour board) which weighs the pros and cons of every treatment strategy.

Before surgery, the anaesthesia team will also assess your fitness for surgery and advise you on various aspects of general anaesthesia and pain control after surgery.

Specialist nurses will also provide pre-surgery counselling.

Colorectal Cancer - Post-surgery care

After recovering from surgery, you will be given regular outpatient appointments to see your team of doctors. These visits may include blood tests and scans to monitor and check if the cancer recurs.

It is important to follow your doctor's advice, keep to scheduled clinic visits and do the prescribed tests so that timely treatment can be administered if the cancer or other problems arise.

Colorectal Cancer - Other Information

  • For more information, click here for the English publication on Colorectal Cancer.
  • For further enquiries on Colorectal Cancer, please call the Cancer Helpline at (65) 6225 5655 or email to

  • To join our support groups, please click here.

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