Colon Cancer

About colon cancer

Colon cancer is an uncontrolled growth in a cluster of gland cells in the lining of the colon (large colon) or rectum. These cells spread into surrounding tissues and can travel to other parts of the body through lymphatic channels and blood vessels.

Why does colon cancer occur?

Colon cancer occurs when damage to the genes of cells lining the colon result in a loss of control of cell growth. This uncontrolled growth procedures a lump (or "polyp") in the lining of the colon which can eventually progress to a cancer.

Who gets colon cancer?

Australia has one of the highest relates of colon cancer in the World. Some of the genetic abnormalities that result in colon cancer can be inherited. If you have one first degree relative with colon cancer, your risk is nearly doubled. If you have two first-degree relatives with colon cancer your risk is nearly trebled. Despite this, most people who get colon cancer do not have any relatives with the disease. In all cancers there are abnormalities of the genes in the cells of the tumour. These abnormalities can either be inherited from a parent of acquired during a person's lifetime.

A person with a gene that causes colorectal cancer can pass the gene to either a son or daughter even though that person never actually developed cancer. This is because some genes are not always "expressed".

The strongest identified inherited risk for colorectal cancer is known as Familial Adenomatous Polyposis (FAP) where multiple polyps develop in the colon and rectum. Cancer develops at an early stage in this condition so family members must be tested whilst still young.

The responsible gene (APC gene) now has been identified and can be found on a blood test which is available in most countries.

Can I prevent colon cancer by eating carefully?

While there is some evidence that a diet high in fresh fruit and vegetables and low in animal fats may reduce your risk of colon cancer and a number of other diseases, no diet can completely eliminate your risk of colon cancer. Dietary factors potentially related to the incidence of colorectal carcinoma are high fat and low fibre consumption.

How do I know if I have colon cancer?

Colon cancer usually does not cause any symptoms until it has been present for some time. Once the tumour is of sufficient size, it can cause symptoms such as bleeding or anaemia, change in colon habit or blockage of the colon. Cancer rarely causes pain unless it has grown through the wall of the colon. By this time, the cancer is usually at an advanced stage.

Can colon cancer be prevented?

Yes. More than 95% of colon cancers begin as a benign (non-cancerous) growth in the lining of the colon called an adenomatous polyp. Except in people with a large inherited risk or with colitis, these polyps usually take several years to progress into cancer. If they are found and removed before this occurs, cancer will not develop.

How do I know if I have colonic polyps?

The vast majority of colonic polyps cause no symptoms at all. Occasionally they will cause a small amount of bleeding or mucus. The only way to know if you have polyps is to look for them. Polyps are protrusions arising from the lining of the colon or rectum. These could be due to an overgrowth of abnormal cells called an adenoma.

Adenomas have a risk of becoming cancerous especially if large, multiple or dysplastic (abnormal cells). If these adenomas are identified before they become too large they can be removed by means of colonoscopy which prevents a cancer from forming. Larger polyps require surgery for removal.

How are polyps found and removed?

Polyps are found with an examination called colonoscopy. A flexible tube with a tiny video camera on the end is passed around the colon under mild sedation. Polyps are seen on a TV monitor and can be removed at the same time through the colonoscope.

Who should be screened?

Screening for a disease means testing people who have no symptoms or signs of the disorder in the hope that if the disease is present it will be diagnosed at a stage which is curable.

Techniques for screening for colorectal carcinoma include testing the colon motion for traces of blood (faecal occult blood), examination of the rectum and the lower end of the large colon (colon) using a flexible instrument (sigmoidoscope), complete colon and rectum examination (colonoscopy) and genetic testing.

Should I have a colonoscopy?

You should have a regular colonoscopy if you have a positive faecal occult blood test or if you have one first degree relative with colon cancer, or if you have colitis. You should also have a regular colonoscopy if you have had polyps or colon cancer in the past.

Will I die if I get colon cancer?

Almost 60% of people with colon cancer can be cured. The earlier the cancer is detected the greater the chances of cure. Once cancer has spread beyond the colon, cure becomes more difficult but other forms of treatment such as chemotherapy can be of assistance.

How is colon cancer treated?

The primary cancer in the colon is treated by surgical removal of the section of the colon involved by the cancer. Usually it is possible to join the ends of the colon together. Very occasionally it may be necessary to create a colostomy where the colon comes onto the abdominal wall into a bag. Generally this is only necessary for cancers very close to the anus. In some circumstances, surgical excision is followed by a course of chemotherapy or radiation.

For more information, please review the Colorectal Cancer Screening Guidelines.

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