Public Health Meets Policy: Colon Cancer Screening

It's fitting that during Colorectal Cancer Awareness Month there is an intense discussion in the medical and regulatory communities and elsewhere about whether we should offer Medicare patients the option of a new screening test for colorectal cancer.

The test is called CT colonography, or virtual colonoscopy. In short, it is a CT scan that can find polyps and cancers in the colon with X-rays.

As of now, the odds are against Medicare coverage for this test. But there is still time for the Centers for Medicare and Medicaid Services (which runs the Medicare program) to review comments from interested parties and perhaps reconsider its recent preliminary "noncoverage" decision.

Should Colon Screening Go Virtual?

I previously wrote about CTC in 2007 when an article was published in the New England Journal of Medicine that supported the use of this test as an alternative to traditional colonoscopy for colorectal cancer screening. Another article published more recently in September 2008 reported on the results from a carefully done trial in which CTC was compared with traditional colonoscopy as a screening test, and fared well.

In March of 2008, the American Cancer Society published new guidelines for the prevention and early detection of colorectal cancer. The society was joined by other professional organizations in writing the guidelines.

One of the key recommendations in the report was that we should favor tests that can prevent colorectal cancer, primarily through the detection of precancerous polyps which, when removed, do not go on to become cancers. It was in this vein that CT colonography was recommended as another option to find these pre-cancerous polyps as part of those guidelines.

But, despite this recommendation, concerns about CTC have persisted.

One key issue surrounding CTC is that if a suspicious polyp or lesion is found on the X-ray, then the patient still has to undergo a traditional colonoscopy to remove the polyp or biopsy the abnormal lesion.

Some centers can do this immediately "on demand." But many cannot, so it means the patient would have to undergo another bowel cleansing and colonoscopy on a different day. Going through a bowel prep for colonoscopy -- whether CTC or traditional -- is not anyone's idea of a fun time.

The good news is that with improving technology, CTC has become much more effective at finding polyps that are more commonly associated with a higher risk of becoming cancer. And that technology continues to improve.

Test Has Pros, Cons

Unlike traditional colonoscopy, a CTC does not require anesthetic and has a much lower risk of perforating the bowel, which can happen with the traditional study more often than most people realize.

On the other hand, CTC can be an uncomfortable test. It requires that air be forced into the colon while the patient lies on his or her stomach. Some people find that actually painful. There is also concern about the radiation dose associated with CTC.

Looming over all this is the fact that CTC is essentially a CT scan, and CT scans of the abdomen will find other things that may or may not be significant. That could lead to further diagnostic tests and surgery that might otherwise not have been needed for something that would never have caused a problem for the patient.

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