Keep Patients Out of My Office, Says CRC Doc

John L. Marshall, MD


September 13, 2011

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Good morning everybody. It is John Marshall from Medscape. I wanted to go back to talking a little about science, and specifically, I want to look at screening for colon cancer. This is a really controversial topic, although we think we have it all settled.

Let's start with what a good screening test really is. First, it needs to be inexpensive. It needs to be safe. It needs to have acceptable sensitivity and specificity. We don't want a lot of false positives and false negatives to require more tests or give us false reassurance. It needs to critically reduce mortality. It needs to actually work, so if you pick the cancer up early when screening a big population and find something, it will improve mortality.

What are the rules for colon cancer? Right now in the United States the standard is that everyone should have a colonoscopy at the age of 50. Colonoscopy does not meet a lot of the criteria for a good screening test. It is not cheap. It is not easy. It is pretty safe, although it still has a low level complication rate. Does it improve mortality? A few studies have hinted that colonoscopy does improve mortality. We say that we don't know that, because we have not done the right clinical trials in the United States. That is what we are really after.

We do not have a patient population that is compliant with screening. They don't have their colonoscopies. Only about one third of the insured American public actually has a colonoscopy at the age of 50 or older, so our compliance rate is terrible. Other parts of the world have approached this differently. They are still embracing the sigmoidoscopy. A few years back, a very controversial clinical trial in England showed that a single sigmoidoscopy at the age of 50 was a good test. It reduced mortality and did not need to be repeated. All you needed to do was one colonoscopy and it met the criteria for a good screening test.

A new study just came out that I first saw on Medscape. This is an Italian study from the Journal of the National Cancer Institute[1] here in the United States. It was a huge study that looked at many hundreds of thousands of patients -- starting with 236,000 patients. The study showed that a single sigmoidoscopy somewhere between the ages of 55 and 65 years actually reduced mortality and did not need to be repeated. Here is yet another study saying that maybe sigmoidoscopy is more in the spirit of what we are after for a true screening test.

That is one way to encourage people to be screened. Sigmoidoscopy may be as good as anything. Of course, we will have our value discussion that we can never get away from. A sigmoidoscopy is a lot less expensive than a colonoscopy. If I were a policymaker, I might say that right now the evidence says "pay for at least one sigmoidoscopy for all patients, particularly in the Medicare population if they have not already had one." We need to prove that colonoscopy is worth the added expense and effort and that it does a better job than sigmoidoscopy.

I also want to introduce another approach -- a laboratory-based approach. A blood test has been developed by Quest Diagnostics (Valencia, California) called the ColoVantage™. Basically, it is a blood test looking for a methylated gene called septin 9. This gene is present only with early tumors. This test is not preventive; it is about early detection, and the test is only for patients who have refused any sort of bowel evaluation (colonoscopy or sigmoidoscopy). ColoVantage™ has a narrow niche, but patients in our world would rather have a blood test than a colonoscopy with the bowel preparation or handle their stool for a stool test.

New techniques are emerging, so we should keep thinking about this issue. Make sure your patients are screened. Colonoscopy is perfectly fine. I am very supportive -- I have had a colonoscopy. As a policy, however, the data are emerging that sigmoidoscopy, maybe even a single test, may be a useful tool. It might improve our patients' compliance. Then, for those who either can't or are not going to be compliant, particularly in primary care, you should know about this blood test that is available. Keep people out of my office. Make sure they are screened. Early detection does matter in colon cancer, and prevention is even better. This is John Marshall for Medscape.


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