Colorectal Cancer (also known as bowel cancer or colon cancer) is cancer found in the colon or rectum (part of large intestines).  Most colon cancers start as a growth on the inner lining of the colon called polyps.  Over time, these polyps can change into cancer.

Factors which can increase chance of polyps progressing to cancer include:

• If the polyp is larger then 1 cm
• If more than 2 polyps are found
• If the cells in the polyp show pre-cancerous changes called dysplasia

How does the colon look like?

The colon is around 5 feet long for undigested food to pass through before coming out as waste. The first section is called ascending colon, the second section is the transverse colon and the third section is the descending colon.  The last 2 sections are the sigmoid and rectum where the waste products sit and wait before being excreted as stools.  If you are constipated, the waste sits here for longer period of time.

What are the risk factors for developing colon cancer?

Although around 75% of colon cancers have NO identifiable risk, these are some of the risk factors which can increase your chance of developing the cancer; 

• Increasing Age. Most colon cancers start after 50 years old
• Unhealthy diet. Long term consumption of red meat or processed meat as well as high-temperature cooking such as barbecuing and pan-frying
• Low fibre intake. Constipation increases the time toxins remain in contact with the colon.  Plant based diet or whole grains are more healthy
• Smoking.  Smoking increases the risk of colon cancer and chance of dying from colon cancer
• Family history.  The increase in life time risk related to family history ranges from 2-6 fold.  Risks are greatest in relatives of patients diagnosed in two or more affected relatives or relatives of patients with colon cancers
• Obesity.  Being overweight, having high fat diet and physical inactivity increases the risk of colon cancer
• Chronic inflammatory intestinal diseases such as Crohn’s disease or ulcerative colitis

Click to view Institute of Cancer Genetics video on Colon Cancer

Symptoms of Colon Cancer

Many people may not have any symptoms at the early stages of colon cancer.  These are some of the more common symptoms to look out for;

• Change in your bowel habit (which may be diarrhoea or constipation or a change in the consistency of the stool)
• Rectal bleeding or blood in the stool
• Abdominal discomfort or feeling bloated
• Feeling of wanting to pass motion all the time
• Unexplained weight loss
• Tiredness or fatigue

How does Colon Cancer spread?

Over time, a polyp can grow into the wall of the colon, then deeper into the layers of the wall and finally into blood vessels or lymph nodes. Metastasis occurs when cancer cells break away and spread to other parts of the body via the blood or lymphatic system. The chance of surviving cancer gets LESS with each increasing stage.

Stages of Colon Cancer

Staging is a standardised way to describe the cancer spread in relation to the wall of the colon or rectum, nearby lymph nodes and other organs.  The AJCC (American Joint Committee on Cancer) and TNM system based on Tumour (T), Lymph Nodes (N) and distant Metastasis (M), are commonly used to describe the cancer stages.  Cancer staging in an important factor in determining your treatment options and your prognosis. 

Why is it important to screen for colon cancer?

It is important to undergo screening for colon cancer because detecting colon cancer EARLY increases the chances of survival. Late stage cancers (such as stage III or IV) have a worse prognosis. In fact, at the polyp stage, the removal of polyp eliminates the chance of it progressing to the later stages of cancer.  Screening is the testing of asymptomatic individuals to determine the risk of developing colon cancer and surveillance is the ongoing monitoring of individuals who have an increased risk for the development of the disease.

Those who have had polyps or cancer treatment in the past, should also arrange for one or two yearly screening/surveillance.  The screening of colon is by using a flexible endoscope called colonoscopy.

Screening lowers the incidence and mortality of colon cancer especially if detected at an early stage and treated early.  Contact a Gastroenterologist or Colon-Rectal Surgeon for a Screening Test

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