Wednesday February 21, 2007
Early detection vital
By DR MILTON LUM
Colorectal cancer is the most common cancer in males and the third most common cancer in females in Peninsular Malaysia.
THE food and liquids that we drink are digested and absorbed in the stomach and small intestine. Undigested food, waste products and water then passes into the large intestine (colon), which is about 150cm long. Some water and salts are absorbed back into the body in the colon, which leads into the rectum. Faeces are stored in the rectum, which is about 15cm long, before they are passed out from the anus.
The lining of the colon and rectum comprises cells which are constantly renewed. Sometimes there is an excessive growth of cells forming a polyp. Most polyps are non-cancerous (benign). However, some polyps may, over time (usually years), develop into cancer.
Cancer can arise anywhere in the large intestine but is commonly found in the descending and sigmoid colon or the rectum.
Colorectal cancer is a common cancer in many countries. According to the second report of the National Cancer Registry 2003, colorectal cancer is the most common cancer in males and the third most common cancer in females in Peninsular Malaysia.
Risk factors
The risk factors include age of 50 years or more; a family history of cancer of the colon or rectum; a personal history of cancer of the colon, rectum, ovary, endometrium or breast; a history of non-cancerous polyps in the colon; a history of ulcerative colitis; certain inherited conditions like familial adenomatous polyposis and hereditary non-polyposis colon cancer; and a diet that comprises plenty of red meat and small amounts of vegetables, fruits and fibre.
Stages
The stages of colorectal cancer are:
Stage 0 – the cancer is found in the innermost lining of the large intestine only.
Stage 1 – the cancer has spread beyond the innermost lining to the second and third layers and involves the inside wall of the large intestine, but it has not spread to the outer wall or outside the large intestine.
Stage 2 – the cancer has spread outside the large intestine to nearby tissue but it has not spread to the lymph nodes.
Stage 3 – the cancer has spread to nearby lymph nodes but it has not spread to other parts of the body.
Stage 4 – the cancer has spread to other parts of the body like the liver or lungs.
Diagnosis and assessment
The symptoms include a change in bowel habits; diarrhoea, constipation or a feeling of incomplete emptying; bright red or very dark blood in the stools; stools that are narrower than usual; general abdominal discomfort like bloating, fullness, frequent gas pains or cramps; unexplained weight loss; constant tiredness or vomiting.
After taking a history and performing a physical examination, which includes a digital rectal examination to feel for lumps or abnormal areas in the rectum, your doctor will carry out tests and procedures to help in the diagnosis and to stage the condition.
Those who are at increased risk will be advised to have screening tests done even though they do not have any symptoms. Such tests would include a faecal occult blood test and/or colonoscopy.
Faecal occult blood test examines the stools for hidden (occult) blood, i.e. it cannot be seen by the naked eye. This test does not say whether a person has colorectal cancer as benign conditions like piles, anal tears (fissures) and benign colonic polyps can also result in a positive test. However, its results will help the doctor decide whether an examination of the large intestine (colonoscopy) is needed.
Colonoscopy is a procedure in which a thin, lighted instrument is used to view the entire colon and rectum for cancerous or non-cancerous growths. Any polyp or abnormal areas seen are removed for microscopic examination. The procedure is usually carried out under sedation.
During the procedure, air will be pumped into the colon to ensure a good view. This may cause bloating or a cramp-like sensation in the lower abdomen. The bowel will need to be emptied a day prior to the procedure with the use of a laxative. Colorectal cancer has been found in only about 10% of those who have had a colonoscopy.
A barium enema is an x-ray procedure in which a liquid containing barium, which is a silver-white metallic compound, is inserted into the rectum through the anus. The barium shows up the image of the large intestine on x-ray films.
A sigmoidoscopy is a procedure in which a thin, lighted instrument is used to view the inside of the lower colon and rectum for cancerous and non-cancerous growths. Any polyp or abnormal areas seen are removed for microscopic examination.
Other imaging procedures like chest x-ray, CAT scan and PET scan may also be carried out to detect any spread to other parts of the body. Some or all of the above tests will be carried out, depending on the individual’s condition.
Treatment
There are different types of treatment for colorectal cancer.
The basic treatment is surgical removal of the cancer and the regional lymph nodes for localised disease.
The procedures include local excision, which is removal of very early cancer by colonoscopy; partial removal of the cancer and surrounding healthy tissue (colectomy) and lymph nodes with the healthy parts stitched together (anastomosis); or colectomy and colostomy.
If the two ends of the colon or rectum cannot be stitched back together, an opening (colostomy) is made on the outside of the body for the stools to pass through. Sometimes, the colostomy is needed only until the lower colon has healed and then it can be reversed. If the entire colon or rectum needs to be removed, then the colostomy will be permanent.
Even if all the cancer that can be seen at the time of the operation are removed, some patients may be offered chemotherapy to destroy any cancer cells that may be left. The medicines are given by mouth and into the veins.
Radiotherapy may be given externally or internally with radioisotopes inserted through thin plastic tubes into the area where there are cancer cells.
After treatment, a substance which may be increased when colon cancer is present (carcinoembryonic antigen – CEA) is measured together with other tests to check if the cancer has come back.
If detected and treated early, the cure rates of colorectal cancer are high. Cure rates of 90% have been reported with early detection.
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