Introduction
Colorectal cancer, or bowel cancer, refers to a cancer in any part of the large bowel. Colorectal cancer is the second commonest cancer in Australia in both men and women, with 1 in 13 Australians developing bowel cancer in their lifetime. Colon cancer is more common than rectal cancer. Colorectal cancer develops in a way similar to cancer in any part of the body, that is where body’s cells multiply in an uncontrolled fashion and form tumours. In colorectal cancers, these tumours form in the lining of the colon or the rectum and usually begin as a 'polyp', a small bump or protrusion in the colon lining. Most polyps are not cancerous, however a small proportion may become cancerous.
Symptoms
In the early stages of colorectal cancer, the symptoms may be subtle. Symptoms may include:
- Iron deficiency or iron deficiency anaemia.
- Bleeding from the rectum / anus.
- Any changes in toilet habit such as the development of diarrhoea / constipation.
- Abdominal pain – this generally only occurs at an advanced stage where a tumour has penetrated the lining of the colon.
Causes
Although medical science understands much of the process of the development of colorectal cancer, it is not yet fully understood exactly what causes it. A number of risk factors for the development of colorectal cancer have however been identified. These include:
Family history
Any close family history of colorectal cancer may increase the risk of someone developing the condition. This is mainly relevant to first-degree relatives (ie. mother, father, brothers or sisters) under the age of 50 who have had colorectal cancer, or many other close family members who have been diagnosed with colorectal cancer at any age. It is important to note that most people who develop colorectal cancer do not have any family history at all, and this is because the relevant genes need to be 'expressed' or turned on by other general lifestyle related factors (see below). The majority of bowel cancers in Australia are not related to family history, even where one exists. There are known inherited colorectal cancer syndromes, such as Familial Adenomatous Polyposis Sydrome (FAP) or Hereditary Non Polyposis Colorectal Cancer (HNPCC), which increase the risk of colorectal cancer significantly, however these conditions are rare.
Lifestyle / Diet
There is a large volume of evidence that indicates that a diet high in fibre – such as wholegrains, fruit, vegetables and nuts – reduces the risk of colorectal cancer. Red meats, smoking, obesity and lack of physical activity increase the risk of colorectal cancer.
Tests & Diagnosis
There are two tests used to check for the presence of polyps / colon cancer:
Faecal Occult Blood Test (FOBT)
This is performed using a faecal sample which is sent away to test for the presence of any blood in the faeces. This blood may be not detectable by the naked eye (i.e. hidden, or 'occult'). Where blood is detected, the next test is a colonoscopy. FOBT’s are mailed out by the government every 2 years to every Australian between 50 and 74 yrs old, and are also widely available at pharmacies, pathology rooms and organizations such as Rotary.
Colonoscopy
A colonoscopy is an inspection of the lining of the colon using a special flexible camera. It is the most sensitive method of detecting a bowel cancer or precancerous polyps. In some cases, a sigmoidoscopy may be recommended – this is similar to a colonoscopy however only involves examining the lower section of the large bowel and rectum.
Treatment
Once a bowel cancer has been diagnosed, surgical removal of the section of bowel affected by the cancer is the most effective treatment. Over 95% of bowel cancers can be treated successfully with surgery if they are detected early. Read more about colorectal cancer surgery here.
