Overview

What is Colorectum Cancer?

Colorectal cancer is a cancer that develops from the cells of the large intestine. The large intestine is made up of the colon and rectum. The rectum comprises the last 15cm of the large intestine and lies within the pelvis which is made up of the hip bones. This is a very small area and the distance between the cancer and the surrounding normal organs is very short. Hence, the chance of the cancer spreading to neighbouring organs in the pelvis is significant.

The colon forms the rest of the large intestine which lies above the level of the hips. It is surrounded by fatty tissue, called omentum, and anchored by more fatty tissue, called mesentery, to the walls of the abdominal cavity. In the mesentery are the lymph glands.

Cancer can develop from the cells lining of the large intestine. The cancer can cause blockage of the intestine, or bleeding into faeces.

How common is Colorectum Cancer?

Colorectum cancer is now the commonest cancer in Singapore affecting both males and females. There were about 1580 cases were diagnosed from 2005-2009 locally.

Age of Onset

Most persons diagnosed with Colorectal cancer are older than 45 years of age. Younger persons, less than 20 years of age, if diagnosed to have Colorectum cancer are likely to be hereditary form of Colorectum cancer, such as familial adenomatous polyposis.

Causes and Risks

The risk of colorectal cancer is increased when there is: 

• A personal history of previous colorectal polyps or colorectal cancer;
• A personal history of inflammatory bowel disease such as ulcerative colitis;
• A family history of colorectal cancer and/ or familial adenomatous polyposis or hereditary non-polyposis colorectal cancer.

Symptoms

Symptoms and Signs of Colorectum Cancer

Common symptoms persons have are a change in bowel habits, such as persistent diarrhoea or constipation or a change in the frequency of stools. Passing blood mixed with stools is also suspicious sign which always needs prompt medical attention.

Other symptoms include persistent ill-defined abdominal discomfort or pain. Occasionally a mass is felt in the abdomen.

Diagnosis

Diagnostic Tests

The simplest way to detect a rectal cancer is by insertion of the doctor's finger into the rectum, i.e. a rectal examination. This can be done in the outpatient clinic, takes less than 5 minutes and causes minimal discomfort. However, this detects cancers only in the last 5 to 8 cm of the rectum.

For cancers which are more distantly located in the large intestine, sigmoidoscope or colonoscope examination can be performed. These fiber-optic flexible tubes are inserted up the rectum into the colon. Through these scopes, removal of a small piece of growth for testing is possible. Insertion of these scopes are performed with minimal anaesthesia in an outpatient clinic. Although uncomfortable, the procedure lasts less than 30 minutes.

Barium enema is an x-ray examination performed to examine the whole length of the large intestine. A dye is passed through a narrow tube into the rectum and allowed to coat the length of the intestine. Multiple x-ray films are taken on various portions of the large intestine and abnormal areas identified. The doctor may further proceed to do a colonoscopy or a sigmoidoscopy so that a biopsy of these suspicious areas can be done.

Treatment Options

Treatment of Colon Cancer

The mainstay of treatment is surgery. The cancer, its surrounding fat and lymph glands are removed during surgery. The two ends of the cut section are joined together. If for some reason the colon cannot be joined, an artificial opening for the colon, called a colostomy, may be required. This opening allows waste to be removed from the body when the normal opening cannot be used or has to be removed. A colostomy may be temporary or permanent.  

Depending on the stage of the cancer, chemotherapy may be required after surgery to improve a person's chance of cure from cancer. Chemotherapy involves injections of anti-cancer drugs into a vein on the hand. Chemotherapy, which lasts from 6 to 12 months, is usually associated with mild mouth ulcers, mild diarrhoea, mild hair loss, possible darkening of complexion, and nausea. The commonest medicine used is 5- fluorouracil, though other drugs may be used in addition.

Treatment of Rectal Cancer

Again, the mainstay of treatment is surgery. Because of the position of the rectum in the bony pelvis, the chance of cancer spreading to the surrounding organs, such as bladder, uterus and bone, is high. Even if the cancer was totally removed by surgery, occasionally there is concern that undetectable cancer cells may lie in the vicinity since the distance between cancer and normal tissue is so short. Hence, depending on how far the cancer has invaded the surrounding fat and organs, radiation therapy is sometimes used to reduce the size of the colorectal cancer before surgery. More often, it is used after surgery to destroy any remaining cancer cells and prevent the cancer from recurring.

Radiotherapy involves giving high-energy rays into a small area where the original cancer was. The course of treatment, given daily for 5 minutes, usually lasts 5 to 6 weeks. Side effects which may occur include diarrhoea, tiredness, skin redness and rash. In some women, radiotherapy brings on early menopause.

As with colon cancer, chemotherapy may also be required, after surgery. Radiotherapy may be given together with chemotherapy.

Prognosis of Colorectum Cancer

Prognosis means the probable outcome of an illness based upon all the relevant facts of the case. All findings from clinical examination and x-ray investigations and pathology reports are important and must be considered together to decide what the progress of an individual case of Colorectum cancer may be. From this, the appropriate course of treatment can be decided and put into action. The treatment strategy will vary from person to person. With prompt and appropriate treatment, the outlook for a person with early Colorectum cancer is good.