Health Guide

High Risk of Colon Cancer

The exact cause of colorectal cancer is unknown. In fact it is thought that there is not one single cause of colorectal cancer. It is more likely that a number of factors, some known and many unknown, may work together to trigger the development of colorectal cancer.

There are certain risk factors that have been identified which may increase a person's risk of developing colorectal cancer. However, having one or even several of these characteristics does not mean that a person is certain, or even likely, to develop colorectal cancer.

Knowing the risks

Average Risk Groups:

Age

Increasing age is considered a major risk factor for developing colorectal cancer. Colorectal cancer is rare in people under 40. The risk increases after the age of 40, rising sharply and progressively after the age of 50.

Dietary factors

It is estimated that rates of colorectal cancer could be reduced in western populations by up to 35% through changes to the food we eat. A diet that is high in fat and low in fibre and vegetables has been linked with an increased risk of colorectal cancer. There has also been an association made between heavily browned or charred meat and colorectal cancer. Excessive alcohol intake and a diet low in calcium have also been implicated.

Behavioural and lifestyle factors

An inactive lifestyle, obesity and smoking have been associated with an increased risk of developing colorectal cancer.

Background

People in western countries such as Australia, America and New Zealand have a higher incidence of colorectal cancer than people in Asian or African countries. This may partly be due to differences in diet.



High risk groups

High risk groups contribute about 15% of all colorectal cancer. It is important for people at high risk to be identified so that cancer can be prevented or if necessary, treated early.

Those with a high risk of colorectal cancer are:

* Individuals with a family history of colon cancer in a first degree relative eg. a parent, sister, brother or child. The risk would be greater if there are two or more affected first degree relatives.
* Those members of families with Familial Adenomatous Polyposis (FAP). People with FAP develop many adenomas (abnormal polyp-like growths) in their bowel and one or more of these adenomas, if not treated, will develop into cancer. FAP usually presents in adolescence and early adulthood.
* Those members of families with family cancer syndrome. These are families where there is the occurrence of various cancers in more than two first degree relatives.
* Those members of families with Hereditary Non-Polyposis Colon Cancer (HNPCC). People with HNPCC have a family history of colon cancer of early onset and are shown to have inherited genetic mutations. Individuals still have polyps but not as many as in FAP.
* People with a history of colon cancer or adenoma.
*

People with long standing chronic inflammatory bowel disease, such as ulcerative colitis or Crohn's disease.