Cancer affecting the rectum is exactly the same disease process as that affecting the colon. Below is a copy of the information that can be found in the section entitled ‘Colon Cancer’. Because the conditions are identical, albeit arising within a different part of the large bowel (colon and rectum together), the features pertaining to this disease are exactly the same.
About Rectal Cancer
Rectal 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 rectal cancer occur?
Rectal cancer occurs when damage to the genes of cells lining the rectum result in a loss of control of cell growth. This uncontrolled growth procedures a lump (or "polyp") in the lining of the rectum which can eventually progress to a cancer.
Who gets rectal cancer?
Australia has one of the highest relates of colorectal cancer (CRC) in the World. Some of the genetic abnormalities that result in colon CRC can be inherited. If you have one first degree relative with CRC, your risk is nearly doubled. If you have two first-degree relatives with CRC your risk is nearly trebled. Despite this, most people who get CRC 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 CRC 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 CRC 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 rectal 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 rectal cancer and a number of other diseases, no diet can completely eliminate your risk of rectal 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 rectal cancer?
Rectal 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 bowel habit or blockage of the bowel. Cancer rarely causes pain unless it has grown through the wall of the rectum. By this time, the cancer is usually at an advanced stage.
Can rectal cancer be prevented?
Yes. More than 95% of rectal cancers begin as a benign (non-cancerous) growth in the lining of the bowel 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 polyps?
The vast majority of rectal 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 CRC 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 CRC, or if you have colitis. You should also have a regular colonoscopy if you have had polyps or CRC in the past.
Will I die if I get rectal cancer?
Almost 60% of people with rectal cancer can be cured. The earlier the cancer is detected the greater the chances of cure. Once cancer has spread beyond the bowel, cure becomes more difficult but other forms of treatment such as chemotherapy can be of assistance.
How is rectal cancer treated?
The primary cancer in the rectum is treated by surgical removal of the section of the rectum involved by the cancer. This operation is called an Anterior Resection. Usually it is possible to join the resection ends 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 preceded by a course of chemotherapy and radiotherapy (neo-adjuvant) to decrease the size of the tumour. If there is nodal involvement then surgery is usually followed by a further course of chemotherapy. For more information, please review the Colorectal Cancer Screening Guidelines.