Colon cancer screening is something I used to have to bring up at annual physicals, but ever since
Katie Couric ran video from her own
colonoscopy on her morning show in 2000 there has been
increasing acceptance of colon cancer screening as a do-able and worthwhile preventive measure.
For most people, colon cancer screening should start at 50 years of age since colon cancer before this age is very uncommon. Certainly, if you have a history in your family of colon cancer or other high-risk conditions you should consider starting screening at 5-10 years prior to the age of cancer diagnosis in your relatives.
For people at higher risk to have colon cancer (such as family history of colon cancer, personal history of
Crohn's disease),
colonoscopy is a good choice of screening test. This allows a doctor to visually inspect the inside of your colon, and biopsy any abnormal lesions to determine whether they are at risk to become cancers and to determine the frequency of interval screening
colonoscopies.
For most people, the are a number of
different tests that could be chosen for screening. While Ms.
Couric's educational efforts spurred people to ask about screening, it also seems to have led many people to assume that
colonoscopy is the best or even the only good screening test. This is not correct.
Admittedly, out of all the tests that require bowel prep (a regimen of laxatives that cleanses out the colon for inspection)
colonoscopy is the only one that inspects the entire colon and in which biopsy can be performed at the same time on any polyps or lesions that may be seen.
However, most polyps seen are benign, or only have a 3-5% chance of possibly becoming cancerous over the following 5-10 years necessitating repeat
colonoscopies for surveillance.
This would be great if
colonoscopy was proved to find cancers early enough to save lives. However, it has not.
In fact,
only one type of test has actually been shown to reduce the actual number of yearly deaths from colon cancer. This test involves test for blood in your bowel movements. If done annually, and if a positive test result (blood shown in bowel movement) is followed by
colonoscopy this type of screening has been shown repeatedly over the years to be the only screening method that actually reduces the risk of dying of colon cancer as the cause of death.
Such tests used to require three separate specimens and used a chemical that would turn blue in contact with iron. Since iron is in hemoglobin which is what red blood cells use to carry oxygen, this test could be an indicator of bleeding from a very small, early colon cancer. Unfortunately, due to the nature of the test a positive result could come from rare meat, dental work or taking aspirin.
A more recent test now in use is superior and widely available and covered by insurances. This test is called FIT (fecal immunochemical test) uses antibodies that link only to human hemoglobin that has not been exposed to stomach acids. Thus, the test is both more accurate and less apt to cause false alarms. Also, it does not require any change in diet or medications, only needs one specimen and the specimen can be mailed back to the lab.
This newer test is so sensitive that it has been
found to detect colon cancers over two years before a colonoscopy would find them, even in people at high risk for colon cancer.
Certainly, if I am seeing you for a physical and you are quite convinced that you need a colonoscopy for screening I will be happy to refer you to a good specialist for this. However, in most cases I recommend the FIT test annually as my preference is for the only life-saving test we have to offer.
