Colon and Rectum Cancer – What you should know and How to reduce your risks

Introduction – The incidence is rising!

Colorectal cancer is the number one cancer diagnosed for males in Singapore and number two cancer diagnosed for females in Singapore (Singapore Cancer Registry, Interim Annual Registry Report, Trends in Cancer Incidence in Singapore, 2006-2010). Colorectal cancer cases have increased because of the aging population (chance of getting colorectal cancer increases with age) and also more people are going for screening.

Screening for colorectal cancer is effective because it almost always starts as a small benign growth, known as polyp, in the wall of the colon or rectum and, over a few years grows bigger to become a cancer. (Fig.1)

Fig. 1

Who is at risk?

The risk factors for colorectal cancer are:
• Age over 50 years (but can occur at any age)
• Personal history of colorectal polyps or colorectal cancer
• Personal history of ulcerative colitis or Crohn's disease
• Family history of colorectal cancer
• Genetic syndrome, Hereditary Non-Polyposis Colorectal Cancer (HPNCC) and Familial Adenomatous Polyposis (FAP)
• Physical inactivity
• Low-fibre and high-fat diet
• Obesity
• Excessive alcohol drinking
• Smoking

What are the signs and symptoms of colorectal cancer?

Usually, people with early stages of colorectal cancer may not experience any symptoms. Thus it is important to go for screening even if there are no symptoms. The common symptoms of colorectal cancer are:
• Blood in the stool
• Unexplained weight loss
• Change in bowel habits (diarrhoea or constipation)
• Bloating and feeling of fullness
• Stools that are narrower than normal
• Nausea and vomiting
• Persistent abdominal pain

How is the diagnosis made?

The diagnosis is usually confirmed with a colonoscopy and biopsy of the cancer. 

Fig. 2

Colonoscopy is an outpatient procedure using a flexible endoscope to examine the inner walls of the colon and rectum. The procedure takes about 20 to 30 minutes under sedation and should be done in a hospital by

a trained doctor. If a polyp or growth is seen during colonoscopy, the some tissues are taken out and send to the laboratory to check if it is benign or cancerous. Fig. 2 shows colon cancer as seen during colonoscopy.

Once diagnosis is confirmed, special scans such as CT or PET scans may be ordered by the doctor to study the extent of the disease.

Stage and Prognosis (Fig. 3)

Stage I (5 year survival rate more than 90%)
Cancer cells are found in the mucosa (innermost layer) and submucosa of the colon wall and may also be found to have spread up to the muscle layer of the colon wall.

Stage II (5 year survival rate 60-75%)
Cancer cells are found to have spread through the muscle layer to the serosa (outermost layer) of the colon wall or nearby organs.

Stage III (5 year survival rate 40%)
Cancer cells have spread nearby lymph nodes

Stage IV (5 year survival rate very low))
Cancer cells have spread to organs like lungs, liver and ovary or a distant lymph node.

Fig. 3

How is colorectal cancer treated?

Treatment for colorectal cancer includes surgery, chemotherapy and radiotherapy which may be used alone or in combination.

In surgery, part of the colon or rectum where the cancer is noted will be removed.(Fig.4) After surgery, most patients can lead an active lifestyle and defecate through their anus like normal individuals.

Fig. 4

In chemotherapy, a drug is used to kill the cancer cells before or after surgery. Possible side effects of chemotherapy are nausea and vomiting, loss of appetite, fatigue, hair loss and diarrhoea.

In radiotherapy, x-rays are used to kill the cancer cells before or after surgery. Possible side effects of radiotherapy are diarrhoea, bleeding and fatigue.

How do I reduce my risk of colorectal cancer?

Family history risks, genetic predisposition and risk associated with age cannot be modified except by going for screening. (see screening recommendations below). 

There are however some modifiable factors we can control:

• Avoid or stop smoking

• Exercise regularly

• Maintain a normal body weight (body mass index <25)

• Eat a high fibre, low fat diet

• Avoid excessive alcohol

• Go for screening 

Screening recommendations

Colorectal cancer is curable if detected early. 

Go for colorectal screening if you are 50 years and above even with no symptoms. If you have a history of colorectal polyp or colorectal cancer do not forget to have regular follow-up with your doctor. If you have a family history of colorectal cancer, you should go for screening at least 10 years earlier than the age when your relative was diagnosed with colorectal cancer. 

The recommended screening tests for colorectal cancer are fecal occult blood test and colonoscopy which should begin at the age of 50 years for people with no symptoms and no family history. If you have symptoms described above, consult your doctor early. 

Fecal occult blood test screens for blood in stool that cannot be detected by the naked eye. It is easy and painless as the person just need to submit a stool sample to the laboratory.

The best method is colonoscopy. It is an outpatient procedure using a flexible endoscope to examine the inner walls of the colon and rectum.

This article was contributed to Tab A Doctor by,

By Dr Kum Cheng Kiong, General Surgeon, Center of Screening and Surgery