Saturday, March 7, 2009

Virtual Colonoscopy? Just Say No

The Center for Medicare and Medicaid Services -- CMS -- is asking for public input on whether virtual colonscopy - CT scanning of the colon -- should be a covered benefit in Medicare to screen for colon cancer.

In early 2008, the American Cancer Society (ACS) added virtual colonoscopy as well as stool DNA testing on its list of suggested screening methods for colon cancer. Screening for colon cancer is recommended for all adults 50 years and older. Besides these two options, the others are:

  • fecal stool testing (FIT or FOBT) annually
  • double contrast barium enema every 5 years
  • flexible sigmoidoscopy every 5 years
  • colonoscopy every 10 years

While I understand why ACS recommended adding virtual colonoscopy to its list, I don't agree with them. Although it is not as invasive as a sigmoidoscopy or colonscopy since patients lay on the CT scanner table while an x-ray technician works the machines to allow xrays to peer into the body, the colon preparation as well as the insufflation of air to distend the colon, is still required. Also, there is exposure of radiation which increasingly a question doctors are facing. Is doing a scan worth the risk of radiation exposure and potentially higher risk of cancer?

More importantly, if a colon polyp or growth is seen on the virtual colonoscopy, patients still need to have an invasive procedure - sigmoidoscopy / colonoscopy - to do a biopsy or removal of the lesion in question. At least these procedures don't involve any radiation as the instrument is essentially a fiber optic cable.

With the healthcare crisis upon us and the nation asking itself what is affordable and reasonable and what is not, CMS hopefully will not recommend virtual colonoscopy to be added to its list of covered benefits. While the technology is attractive, there are other proven screening tests that albeit uncomfortable are life-saving and don't subject people to unnecessary radiation.


Joseph Sucher, MD FACS said...


I think that I understand your post. Which is, virtual colonoscopy should not be paid for by insurance because it is too expensive and may not produce any significant benefit. I might agree (but I am not up to date on the particulars in the literature).

However, I am disappointed with your clearly one-sided argument.

First. Why do you only discuss the very unlikely possibility of harmful radiation exposure from non-invasive CT scanning versus the very real potential of complications from invasive colonoscopy? To me, it appears that you are only presenting a one-sided argument. Knowing that 64 slice helical and spiral CT radiation doses are less than that delivered for routine 2 view chest xray. Given that, I don't feel that there is a significant argument to be made of its dangers versus the very real danger of potential iatrogenic perforation from a colonoscope.

Second, you don't talk about the fact that invasive colonoscopy requires conscious sedation which comes with its risks. CT scanning does not require this sedation. Additionally, since there is no sedation required, there is no recovery required.

Third, CT scanning is faster and more efficient for the patient with less discomfort.

Fourth, if you don't have a problem noted on CT then you don't get an invasive procedure. The way you word it in your post, you only look at if you DO have an abnormality on CT then you still need a colonoscopy. Well.... flip it around. If you get a colonoscopy first and DON'T find a problem, then you just subjected yourself to the dangers of I.V. sedation AND and invasive procedure for no therapeutic benefit.

Therefore, I think that overall, your argument is one-sided and can be debunked if we simply argue on your points alone. However, I am not an expert on the current evidence of virtual colonoscopy, and therefore reserve my final judgement of its worth based on that.


Davis Liu, MD said...

Dear Dr. Sucher:
Thanks for the comments.

The evidence for virtual colonoscopy at this time isn't solid. The USPSTF doesn't believe their is adequate evidence to recommend. Initially findings were not reproducible outside the original group from the University of Wisconsin. CT scans have never been approved by FDA for screening tests. Total body scan radiation typically is equivalent to 150 chest xrays (perhaps virtual colonoscopy total radiation is less. Don't know about 64 slice CT, but would appreciate the source about it has less radiation dose than a routine 2 view CXR).

I would say that there are other modalities that are better, albeit perhaps more uncomfortable than virtual colonoscopy. I understand from an advocacy position of the American Cancer Society and why they would recommend virtual colonoscopy in addition to stool DNA testing (which is less appealing and I don't recommend because it requires packaging an entire bowel movement?! It is difficult enough to have patients do stool smears for FIT).

Nevertheless, until research shows virtual colonoscopy is as proven as the other modalities and the question of radiation is better answered, I think patients, insurers, and the government should hold off on this technology for now. For full disclosure when counseling my patients about colon cancer screening, I detail all the options. None have opted for virtual colonoscopy. The majority favor FIT and flexible sigmoidoscopy.

Michael said...

Dr. Liu,

I definitely understand where you are coming from. However, I would challenge the statement that the evidence isn't solid. For example the ACRIN trial was able to confirm a 90% sensitivity with regards to polyps and lesions greater than 10 mm, which is equivalent to optical colonoscopy. This was a 15 site trial. Additionally the recently published BCBS TEC Assessment of CTC found that the procedure meets the criteria to be considered an acceptable screening test for colorectal cancer.

With regards to radiation exposure, this is definitely a concern. However, the average lifetime risk of contracting CRC is 6%, and that the risk of contracting cancer due to radiation exposure from CT scanning is less than .1%. Add to that the fact that 1 in 1000 people will experience some damage to the colon (i.e. perforation) during an optical colonoscopy, and I think we can see the benefits of CTC.

Lastly, I understand the concern that a patient may go through the CTC procedure, and then have to still have to receive a colonoscopy. But, we have to remember, 80-90% (depending on the report) of all patients will test negative, and not require further examination. For those that do test positive, some GI facilities are beginning to look at having both a CT and an endoscopy suite. That way, when a patient tests positive, they can go straight to the endoscopy suite and not require any additional prep or have to make another appointment.

I definitely don't want my argument to sound entirely one sided (which I'm sure it does). In the end, what it comes down to is getting people in the at-risk population to get screened through one method or another. And it will continue to be physicians like yourself that encourage their patients to get screened through any means necessary. I urge you to look at some of the latest findings, and I respect if you still feel that there is more proof needed regarding CTC, and the real risks and costs associated with it.

Davis Liu, MD said...

Dear Deck:

Appreciate the comments. I think it would be helpful for full disclosure that your role is - Field Marketing Manager, Computed Tomography at Philips Medical Systems - and how important it might be for your organization has in whether CMS approves virtual colonoscopy for reimbursement.

Nevertheless, thank you for the other links.

Joseph Sucher, MD FACS said...


The followup on you post has been excellent. You were right to ask for a reference on CXray dose vs CT.

From "Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2 (2006)
Board on Radiation Effects Research (BRER)" in the National Academies Press -

CXray ranges from 0.02 to 10mGy
Whole body spiral CT ranges from 10 to 20mGy.

That measurement of mGy is misleading though. As I looked further, it turns out that I should have payed more attention to the "biologic effect" measurement of Sieverts.

Therefore, currently CXray delivers only 0.1 mSv as listed from multiple sources, and CT colonography specifically delivers 5 mSv. Additionally to put this in perspective, we all our exposed to a background of 3mSv per year of natural radiation exposure.

Very interesting. Thank you for making me learn something better.



Michael said...

Dr. Liu,

While you are right that it wouldn't hurt my organization should Medicare eventually reimburse for a VC procedure, I think it is actually less important. The recommend age for screening is 50, a full 15 years before a patient would be covered by Medicare.

Being that I work for a company that has a stake in the eventual acceptance of VC as an option for CRC screening doesn't make my opinion or credibility less significant. It means that on a daily basis I am reading and researching, making sure that this is something viable, interfacing with physicians. Ultimately, I have the same intersts in you, seeing patients screened through whatever means necessary. I just think that when organizations such as the American Cancer Society, BCBS, and the AGA begin recommending VC (regardless of the vendor), it's something to take note of.

Please, don't disregard my comments just because of who I may be employed by.

Unknown said...


Thanks for your email and comments. I think from an advocacy perspective I understand why virtual colonoscopy is being favored by American Cancer Society, however, in my mind it isn't superior to other procedures that exist. To be fair, I give all of my patients the options including virtual colonoscopy and the pros and cons of each.

The reason the Medicare coverage is important, as you know, is that insurers are far more likely to offer coverage if Medicare covers it. As a result the pool of potentially screened moves from 65 year olds to 50 year olds.

If virtual colonoscopy costs Medicare and insurers far less than current screening methods and is proven consistently to be equally as effective (there was some initially difficulty with reproducing results outside the initial pilot center) and there is some data about cancer risk related to the radiation, albeit small, then I think more doctors may recommend it.

Bill Eastman said...

With a regular colonoscopym polyps can be removed and biospys done. I would think that it would cost less just doing the regular colonoscopy instead of the virtual colonoscopy. I just had a colonoscopy this morningm no polyps, but an area was red so thry did a biopsy. I'd hat to have to do the prep twice. Prep was the worse part.

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Bob S said...

Thanks for your efforts in this informative Blog. My GI doctor is recommending me for VC for colon screening. I am on coumadin for A-fib and had a TIA a short while back when my coumadin INR was subtheroputic. I have to get off blood thinners and risk a stroke for optical exam screening that is covered by Medicare. I am paying Medicare B and Medigap F. VC is not covered by Medicare or Medigap because of the views that you presented that leave out the patient in this case. There are a lot more people in my predicament who are coming into the system. Bob S


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