|
What is Colon Cancer?
Every living tissue and organ in the body is made up of tiny building blocks called cells. Normal cells in the body grow at a steady and controlled rate. New cells are normally formed to replace worn out cells or to repair injured cells. Occasionally some of these cells proliferate out of control and have the tendency and ability to spread in an abnormal way to other organs and tissues These cells hence use up the body reserves as well as destroy bodily function.
These abnormal cells are called cancer and the growth is an abnormal and uncontrolled group of cells. Cancer thus results in severe general malnutrition and malfunction of affected organs. Moreover cancer cells have the ability to spread beyond the original site of cancer growth Malignant tumors or cancers do not just grow large at the original site of cancer growth; their cells can also travel to other organs and form secondary tumors.
These secondary growths are called metastasis and the ability to form such a metastasis is the hallmark of a malignant cancer. The most feared diagnosis is cancer of the colon. This is the most common cause of cancer in males in Singapore and second most common in females. However. it is also one of the most preventable cancers. Thus. regular screening is important, especially for those at risk.
Colorectal cancer arises from the innermost lining of the wall of the colon and rectum. This epithelia llining is also called the mucosa layer of the large intestine. It's incidence is increasing in developed countries. Symptoms include change in bowel habits, anemia (lack of blood), bleeding and loss of weight. Unfortunately, when these symptoms occur, the cancer is very often advanced and though amenable to treatment, often requires prolonged chemotherapy and multiple operations. This has lead to the concept of SCREENING where people without symptoms are stratified according to their risk factors and screening done. The best form of investigation is still colonoscopy as it is accurate and has a therapeutic potential as it can also remove polyps. Polyps are precursors to cancer.
Presently, anybody above 50 years of age should prefably have some form of screening. The screening should be carried out earlier, usually at the age of 40 or 5 years younger than the index case in people at risk. These include those with :
a) A family history of colorectal cancer or adenoma(polyp)
b) A history of ulcerative colitis or other inflammatory bowel disease.
c) Personal history of cancer or polyps or other related tumors/cancers
What are the possible protections against colorectal cancer?
The most useful and fail safe method currently of preventing colorectal cancer is colonoscopy and removal of all pre-malignant polyps present. Removal of polyps help in the prevention of colorectal cancer.
Who are in the high risk groups for large bowel cancer?
People with high risks of colorectal cancer includes those with :
1. a strong family history of large bowel cancer or other related cancers in first degree relatives.
2. a previous history of adenomas or cancer of the large bowel.
3. a history of chronic ulcerative colitis or Crohn's disease.
Who are in the early symptoms and signs of colorectal cancer?
The colorectum is a hollow muscular tube concerned with allowing digested food and waste to pass through. Symptoms therefore only arise when this smooth passage is disturbed, and because of the elasticity and huge reserve of the large intestine, symptoms are often minimal or occur only late in the disease. Hence, 60% of colorectal cancer patients presenting to hospitals already have lymph node spread or widespread cancer. Symptoms depend on the stage of the disease as well as the location of the cancer in the colorectum. During the early stages of cancer most patients do not have symptoms. The commonest symptom of large bowel cancer is rectal bleeding which occurs in both benign adenomas and cancers. Often however this can only be detected in very minute amounts and cannot be seen with the naked eyes.
As a summary the following may be useful:
1. Blood in the stools.
2. A change from your normal bowel habit usually with looser stools with no
immediately obvious reason.
3. Unexplained loss of weight.
4. Recent onset of abdominal colic.
5. A persistent feeling of still having stools in spite of last having had a bowel motion.
What sort of tests might the doctor do on me?
Generally the hospital doctor will take a detailed account of your medical problems as well as making you relate your past and family history. The doctor will then do a physical examination that must include a rectal examination and a proctoscopy. You may then be asked to do a faecal occult blood test, a blood test as well as be booked for colonoscopy or a barium enema test. If cancer is already confirmed, liver ultrasound or CAT scan may be needed.
Is the carcino-embryonic antigen (CEA) an useful test?
The carcino-embryonic antigen (CEA) is a protein that is easily measured with an inexpensive and simple test. CEA is normally found in low concentrations in embryonic and fetal gut as well as in pancreatic, lung and liver cells. Hence mild elevations may be found in pregnancy, as well as in smokers and in inflammatory and as well as malignant conditions of the respiratory, hepato-biliary and gastrointestinal system.
This test is not done for screening, as it is only helpful after a diagnosis of colorectal cancer is made. However, a raised CEA in a "normal" person must be an indication that the colorectum needs to be investigated further.
What sort of investigative methods are there to examine the large intensine?
Colonoscopy
This is the gold standard for detection of colonic lesions. For this test to be successful, the large bowel has to be meticulously cleaned before the procedure. Most modern laxatives work with the ingestion of two or three liters of plain water and should produce about 2 to 6 loose watery diarrhoea starting within an hour after ingestion of the laxative. A sedative may be given but most patients undergoing colonoscopy have very mild tolerable discomfort and do not require sedatives.
The lack of availability of colonoscopy for everyone; the expense and the small risks involved should not mitigate against those who would prefer a total colonoscopy as a screening test for the detection of colorectal cancer and its precursor polyps. Thus people who have the means and the resources and who understand the risks involved should certainly be allowed to avail themselves to this method of investigation.
What are the different stages of colorectal cancer?
Dukes Involvement 5 year survival
A Not reaching muscular bowel wall 98%
B Invasion of rectal wall, lymph nodes not involved 80%
C1 Regional nodes only, apical nodes not involved 50%
C2 Nodes at point of ligature involved 15%
D Spread to other organs 5 %
I have had colorectal cancer, should all members of my family be screened for colorectal cancer?
It is important that a proper family history of cancer be taken. Especially families where there are a large number of members with colorectal cancer and other families that have a large number of colorectal cancer together with other cancers especially of the urinary system and female genital tract. These two sort of families usually have several members who had the disease when they were very young, less than 40 years of age. Special consideration must be given to the surveillance of members of these two sorts of families for screening at younger ages, than would be applicable to the general population. Special families with high risk for colorectal cancer are families with HNPCC and FAP.
|
General Knowledge & Education