Colorectal Cancer

Colorectal cancer is the most common cancer in Singapore¹. The number of colorectal cancer cases has been steadily increasing in both men and women. Singapore has one of the highest numbers of this cancer in Asia, together with Taiwan, Japan and Australia. Fortunately, the number of deaths from colorectal cancer has been dropping for the last 15 years. This is due to more people going for regular screening which can help find colorectal cancers early. Treatments for colorectal cancer have also improved, becoming more effective especially if the cancer is found early.

¹Singapore Cancer Registry Interim Annual Report, Trends in Cancer Incidence in Singapore, 2010 – 2014, National Registry of Diseases Office (released 26 May 2015)

There is no single cause of colorectal cancer, with colon cancer beginning as a polyp (an abnormal growth) that develops into a cancerous growth. People with certain risk factors are more likely to develop colorectal cancer, these risk factors include:

1. Colorectal Polyps

These are growths on the inner wall of the colon or rectum commonly found in people over the age of 50. While most polyps are benign (not cancerous), some can become cancerous.

2. Ulcerative Colitis or Crohn’s Disease

Ulcerative colitis or Crohn’s disease is a condition that causes the swelling of the colon over many years and can increase the risk of developing colorectal cancer.

3. Personal History of Cancer

A colorectal cancer survivor may develop colorectal cancer a second time. Women with a history of cancer of the ovary, uterus or breast are also at a higher risk of developing colorectal cancer.

4. Family History of Colorectal Cancer

A family history of colorectal cancer can mean a higher risk of developing this disease, especially if the family member or relative suffered from the cancer at a young age.

5. Lifestyle Factors

People who smoke, or have a diet high in fat and low in fruits and vegetables have a higher chance of developing colorectal cancer.

6. Age over 50

Colorectal cancer is more likely to occur to people over the age of 50. More than 90% of these people are over the age of 50.

Common symptoms of colorectal cancer include:

• Change in bowel habits (diarrhoea or constipation)
• Feeling that the bowel does not empty completely
• Blood (either bright red or very dark) in the stools
• Stools are narrower than usual
• Often having gas pains or cramps, or feeling full or bloated
• Unexplained weight loss
• Chronic tiredness
• Nausea or vomiting

Take note that these symptoms can be caused by other health problems and are often not due to cancer. Also, it is important to note that early stage cancer does not usually cause pain and may not have any obvious symptoms. Therefore, anyone with these symptoms should see a doctor to be screened for colorectal cancer as soon as possible.

Screening

Screening tests help your doctor find polyps or cancer before you have symptoms. Early detection of colorectal cancer will also improve the success rates of cancer treatment. The following screening tests can be used to detect polyps, cancer, or other abnormalities.

Faecal Occult Blood Test (FOBT)

Cancer or polyps can sometimes cause bleeding, and the FOBT can find tiny amounts of blood in the stool. If blood is found in the stools, other tests can be done to find the source of the blood. Colorectal cancer isn't the only condition that causes blood in the stool as benign conditions like haemorrhoids can also cause this symptom.

Sigmoidoscopy

The rectum and the lower part of the colon is examined with a lit tube (sigmoidoscope) to look for polyps which may be removed by the doctor.

Colonoscopy

Using a long flexible tube with a camera (colonoscope), the doctor can examine the inside of the intestines and colon. Any polyps are found may be removed during this procedure.

Double-contrast Barium Enema

This involves filling the colon and rectum with a white liquid (barium) that improves the X-ray pictures. This allows polyps and anything out of the ordinary to be seen clearly in the scans.

Virtual Colonoscopy

Special X-ray equipment is used to take pictures of the colon and rectum. A computer then combines these pictures into detailed images to show anything out of the ordinary like polyps and tumours.

If abnormalities (eg. polyps) are found, the abnormal tissue can be removed for a biopsy during a colonoscopy or sigmoidoscopy. A pathologist will later examine the biopsy with a microscope and check the tissue for cancer cells.

How is Colorectal Cancer Assessed?

If the biopsy shows that cancer is present, the doctor will carry out further tests to determine the stage of the cancer. The stage is based on factors like whether the tumour has invaded nearby tissues, whether the cancer has spread and, if so, to which parts of the body.

The Stages of Colorectal Cancer are:

• Stage 0: The cancer is found only in the innermost lining of the colon or rectum. This is also known as pre-cancer, as the cancer cells have yet to develop and spread.
• Stage I: The tumour has grown into the inner wall of the colon or rectum, but not through the wall.
• Stage II: The tumour has grown deeper into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
• Stage III: The tumour has spread to nearby lymph nodes, but not to other parts of the body.
• Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs.
• Recurrence: This is cancer that has been treated and has returned after a period of time. The disease may return in the colon or rectum, or in another part of the body. There is a chance that the recurring cancer is more aggressive than normal.

Surgery

The tissues that contain the tumour, as well as nearby tissue or lymph nodes, can be removed through surgery. This can be done in a traditional open surgery, or by laparoscopy, a minimally invasive technique that involves smaller cuts in the body. 

Chemotherapy

Chemotherapy is the use of drugs to shrink or destroy cancer cells. The drugs enter the bloodstream and can travel to cancer cells all over the body.

Targeted Cancer Therapy

In cases where the colorectal cancer has spread, patients may be given targeted therapy. These are drugs or other substances that affect specific molecules involved in tumour growth, thus stopping or reducing the spread of the cancer.

Radiation Therapy

Radiation therapy, also called radiotherapy, uses high-energy rays to destroy cancer cells in the affected area.