Colon cancer screening
Why is a colonoscopy considered the gold standard?
by Jamal Ross
Having a realization that colon cancer is a serious disease that is largely preventable is half the battle. Once you make the commitment to be tested for colon cancer, there is another challenge to determine which test is best for you. One of the pitfalls of the FIT and multitarget DNA test (trade name Cologuard) is the inability to find polyps. A poly is a small growth on a stalk. Think of a skin tag in your colon. Some polyps are harmless. Others have malignant potential. Polyps that can turn into cancer are called adenomas. An adenoma is the middleman of cancer. As we wrap up our discussion on screening tests we will take closer look at a gold standard, the colonoscopy, which is critical for finding and removing polyps and adenomas.
The colonoscopy is considered the gold standard for a reason. When the FIT and stool DNA tests are positive, this is not the end of the road. Another test need to be performed. This test is a colonosocpy. colon cancer is can be detected, but when these tests are positive this is not the end of the road. This test is a colonoscopy. Also, a colonoscopy can not only pick up colon cancer, but it can also find the middleman of cancer – an adenoma. Even more importantly, adenomas can be removed and treated with colonoscopy. The sample can then be placed under a microscopy and we can find out more information about how aggressive this middleman is. This helps determine your future risk for colonoscopy and how often you would need a colonoscopy. The DNA and FIT studies not only missed the majority of adenomas, but also do not give us any more information about these adenomas if there happen to be found. When colon cancer is found on colonoscopy, a piece of tissue can be taken at the time of the test. This is called a biopsy. Biopsy again helps determine how aggressive the cancer is and which medications may work best against it. There is no option for a biopsy for stool DNA or FIT tests. This is why if the stool DNA or FIT tests are positive, a coloscopy is needed regardless.
Furthermore, a colonoscopy can be performed every 5-10 in those who have normal results. (1) The FIT should be completed every year and the stool DNA test can be done every 3 years. Therefore, the colonoscopy potentially has the longest “time off” for testing than any of the other colon cancer tests if they happen to be normal. This can be seen as a convenience. On the other hand, a colonoscopy is a procedure and cannot be performed at home. Certain medications such as blood thinners, need to be help prior to getting a colonoscopy. Also, you are required to “clean your colon” with a solution that works much like a laxative before undergoing a colonoscopy. As a result, you can have some diarrhea as you clean your colon and this can be seen as an inconvenience. Even more, you cannot have a large substantial meal prior to colonoscopy, so there are dietary restrictions when getting a colonoscopy.
With a colonoscopy, you with require some “twilight” or sedation. You may be in and out of consciousness for the procedure, but many people do not remember the procedure at all after it is complete. A doctor will insert a flexible tube with a camera on the end into your rectum. In this way, the doctor is able to get “eyes on the ground” to look your compete colon. This is why it is important to have a good bowel cleanse, as we do not stool to obstruct the view of the colon and prevent the doctor from getting a good look at what is going on. There is also a tool at the end of this tube the help snip adenoma and obtain biopsies. The stool DNA and FIT tests have no options to get a visual inspection of your colon. Theses stool test are essentially performed in the dark and a negative result on a stool DNA or FIT test does not mean you do not and cancer; and it certainly does not mean you do not have a precancer mass, such as an adenoma.
When it comes to colon cancer tests, we are faced with a decision: Should perform a more convenient test that is less precise compared to an inconvenient test that is the gold standard? The FIT test can be performed at home and require a small stool sample. This is most convenient, but need to be done every year. The multi-target stool DNA test, or Cologuard by its trade name, can also be done at home but requires a large stool sample. The Cologuard test can be completed every 3 years. A colonoscopy needs to be done in a hospital or office and involves some inconvenience of holding medications, changing your diet temporarily and “cleaning your colon” with a laxative. In general, a colonoscopy should be performed as the first test to pick up colon cancer unless someone cannot hold a medication or has a preference to not to have a colonoscopy. Otherwise, “something is better than nothing” It is better to get a FIT test rather than do nothing at all. If you are willing to have some inconvenience, a colonoscopy is the best option to screen for colon cancer as we can find and treat pre-cancerous polyps and determine the need for colonoscopy in the future.
Colon Cancer Series
1. In Alguire, P. C., & American College of Physicians, (2018). MKSAP 18: Medical knowledge self-assessment program.