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By Dr. L. William Lauro
Colon cancer is the second most lethal cancer in America (lung cancer is number one). Each year there are approximately 140,000 new cases of colon cancer and the disease kills about 56,000 people per year. It is the only major malignancy that afflicts men and women about equally. Almost every other cancer has a gender preference. Tragically, this cancer, which causes so much pain, suffering, loss of life, and expenditure of medical resources is really quite treatable and even preventable if it is detected early enough. This is why we place such a high premium on colon cancer screening.
When colon cancer is diagnosed, the likelihood of long-term survival depends mainly on the anatomic stage of the disease found at surgery. If you discover a patient's colon cancer before the symptoms of cancer develops, then most of these patients are curable (five years survival is greater than 80%). Conversely, by the time symptoms occur (such as bowel habit change, rectal bleeding, unexplained weight loss) most colon cancers have already spread beyond the bowel and involve the lymph nodes and other organs. At this point the chance of survival decreases to less than 50%. The primary objective, therefore, in treating colon cancer is to detect these cancers before symptoms appear while there is still an excellent chance for cure.
How Does Colon Cancer Start?
Most colon cancers originate in a colon polyp. A polyp is simply an abnormal growth of tissue on the surface of the bowel mucous membrane (the inside lining of the intestinal wall). Colon polyps may be benign (non-cancerous) or malignant (cancerous). Regardless of type, most of these polyps are silent and have no symptoms until they either grow really large and start causing symptoms or actually turn into cancer and spread throughout the abdominal cavity. Therefore, these polyps can only be detected early on through colon cancer screening.
Who should be screened for colon cancer?
The current recommendations for asymptomatic patients are that every person over the age of 50 has some form of colon cancer screening. Those people who are at higher risk for the disease (i.e. because of family history of colon cancer or because they have had colon polyps in the past or because they have chronic ulcerative colitis or Crohn's colitis) should have their screening done at a much younger age (even in their 20's and 30's). Also, people who have symptoms that suggest colon cancer, even if they are not yet 50 years old, should have a work-up. These symptoms include rectal bleeding, change in bowel habits (where the stool has become either smaller in size, harder, or more liquid), unexplained weight loss, change in appetite, etc.
Screening methods for colon cancer:
There are several methods used to screen for colon cancer. The gold standard is colonoscopy. This is where the physician inserts an instrument up through the rectum and looks at the insides of the entire colon (the left colon or "simoid", the transverse or central colon, and the right colon). The physician is able to visualize polyps and biopsy them right through the scope. The scope is about six feet in length and this procedure is somewhat invasive and uncomfortable. It requires light IV anesthesia. It is usually performed in a hospital or out-patient center designed for these types of procedures. It is moderately expensive. The biggest risk of this procedure is bowel wall perforation, but that is quite rare in the hands of an experienced physician. Colonoscopy is the most accurate test for colon cancer that we have.
Short of colonoscopy, what are the other options?
One test that is very simple, inexpensive, and has been around for years is the fecal occult blood test. This is where the doctor takes a piece of stool (obtained either during a routine physical exam or by the patient collecting a sample at home) and analyzes it for microscopic blood in the stool that is undetected by the eye. However, these tests are not full proof. Some people may have a negative fecal test and yet still have a very early colon cancer. Other people may have a positive test (indicating microscopic blood in their stool) but find out later that it is not coming from colon cancer.
Here is the problem: It turns out that certain foods can interfere with the test. Also, taking aspirin and other anti-inflammatories can cause microscopic bleeding in the intestines and thus interfere with the test. Also, rectal problems such as fissures and hemorrhoids can interfere and turn the test positive. And finally, most cancers, by the time they start leaking blood into the intestines, are quite advanced. Despite its limitations, this test is helpful, cheap, and easy to do but, as I said, it is not full proof. If you have this test performed at a physician's office make sure you take home a few of the fecal occult blood test cards and do several more stool samples at home. Simply doing one test at a physician's office isn't good enough. If your test is positive and there are no obvious reasons for a false positive result, then you have microscopic blood in your stools and you should proceed to colonoscopy.
The next test to consider is flexible sigmoidoscopy. The scope used for this test is only about 18 inches long and is much more comfortable than the colonoscope. As a matter of fact most patients can tolerate having the procedure done without anesthesia. Flexible sigmoidoscopy is highly accurate and much cheaper than colonoscopy. So what then is the drawback? Well, because the scope is so much shorter than the colonoscope it only allows the physician to see about
1 ½ feet up into the left side of the colon (called the rectosigmoid colon). It does not allow the physician to look at the transverse and right side of the colon at all. Granted, about 75% of colon cancers do originate on the left side; however, the remaining colon cancers that develop on the right side will not be detected with flexible sigmoidoscopy. So the 25% of colon cancers that originate on the right side of the colon will not be detected by flexible sigmoidoscopy.
Another test that is available but not used very often anymore is the barium enema x-ray. This is where the physician squirts a barium contrast up through the rectum into the colon and then takes x-rays looking for shadows and filling defects that would indicate polyps. This test is not used very much these days because it is uncomfortable and not highly accurate.
How often should you have tests for colon cancer?
If you have a colonoscopy at age 50 and you have no special risk factors for, or symptoms of, colon cancer then you can wait 10 years for your next procedure. If you decide to just have the flexible sigmoidoscopy test you should be evaluated every 3-5 years. The fecal occult blood test should be performed every time you have a physical, or about every 1-2 years (after age 40).
Colon cancer is a common, deadly, and yet easily treated disease if caught early. Therefore physicians place a high premium on screening for colon cancer. I advocate that every person give serious thought to seeing their doctor for this screening, especially if you are in your forties or older. And my test of choice is colonoscopy every ten years (more often if you have special risk factors or symptoms).
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