M. D. Anderson Cancer Center
Cancer Newsline Audio Podcast Series
Date: April 13, 2009
Duration: 0 / 15:38
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Welcome to Cancer Newsline, a weekly podcast series from the University of Texas M. D. Anderson Cancer Center. Cancer Newsline helps you stay current with the news on cancer research, diagnosis, treatment, and prevention, providing the latest information on reducing your family’s cancer risk. I’m your host, Lisa Garvin. Today, we’re talking with George Chang, an assistant professor in Surgical Oncology and David Vining, who is a professor of Diagnostic Radiology and we’ll be talking about colonoscopy and colon cancer today. Welcome, gentleman. Thank you very much! I think we’ll start with you Dr. Chang, let’s talk about traditional colonoscopy and how it’s used as a tool. Lets talk about that.
Well, traditional colonoscopy involves the use of a fiber optic colonoscope. It’s an optical device that allows endoscopists to visualize the inside of the colon. It’s typically performed by a gastroenterologist; it requires preparation of the colon usually by a cathartic of some sort and then utilizing video technology we’re able to actually image the inside of the colon, see it directly, identify lesions, and biopsy them or remove them. So, it provides an opportunity for us to not only diagnose polyps, which are precursors to colon cancer, but potentially to remove them as well. It is often helpful to have some intravenous sedation so that the examination can proceed more comfortably.
Did you find that, and it is a standard tool, it seems to be one of the most standard screening tools that we have for any type of cancer.
Yes there are a number of well established colon cancer screening tools. Colonoscopy remains one of the mainstays for colon cancer screening. There are additional screening modalities including fecal occult blood testing. We rarely utilize barium enema testing anymore, and more recently CT colonography has become increasingly utilized for colon cancer screening.
What are the recommended screening guidelines for colorectal screening?
In average risk individuals in the United States at the age of 50 your first colonoscopy is recommended, so those individuals between the ages of 50 and 75 should undergo colon cancer screening with colonoscopy every 5 to 10 years. Fecal occult blood testing should be performed annually if that’s the modality that’s utilized. For CT colonography we’ll be learning a little bit more about that as well; the intervals are likely to be similar with colonoscopy. Now, although I say that, these are the typical guidelines, those individuals with an increased risk, those with a family history for one of the colorectal cancer syndromes, for example, should undergo colon cancer screening earlier. Also, those individuals who have first degree relatives with colon cancer, at a young age should undergo screening. So, if your first degree relative, such as your mother or father, had colon cancer diagnosed at 50 or 55, then the first colon cancer screening test should be performed ten years earlier at 40 or 45. Also although the guidelines call for screening between 50 and 75, for those individuals who may be 75 or older, who are physiologically much younger, then it may be appropriate to continue the screening.
Are there any ethnic groups that have certain risk factors, like African Americans? Are they more likely to have colon cancer?
Well, there has been the suggestion that there may be an earlier age at onset for African Americans, for example, and so some would advocate screening at an earlier age but that has not worked its way into the standard guidelines at this time.
Let’s talk about the advantages of traditional colonoscopy. What are the advantages of the test?
Well, first of all, the advantage of any screening modality is early detection, and with early detection we have an opportunity to treat precursor lesions, such as polyps or cancers, at an earlier stage. In comparison to CT colonography, for example, an advantage of colonoscopy would be the opportunity for direct diagnostic evaluation. If there is a lesion that is identified, then it can be biopsied at the time of colonoscopy. Another advantage is the opportunity to remove lesions that are precursor lesions, such as polyps, that do not have an association with cancer. We think that colon cancer arises from progression of colon polyps, and by removing the polyps, we can prevent the development of colon cancer.
What are some of the disadvantages? Obviously, some people don’t like being knocked out and having a long tube, you know, stuck inside their body but what are some of the barriers or disadvantages to traditional colonoscopy?
Well, one of the difficulties for patients with having the screening examination is the need for the cathartic, for the bowel preparation. So, that is a disadvantage of any of the direct visualization techniques. Another disadvantage of colonoscopy versus some of the other modalities is the need for sedation. Most patients benefit from sedation in order to make the examination more comfortable. That would require that a family member or friend accompany you to the examination and drive you home that day. It does require the need for an IV, and all of those things can be potential disadvantages to colonoscopy. There are potential complications associated with the procedure itself although the procedure is very well tolerated in general and generally very safe.
Great! Dr. Vining, we’ll now tune to you. This is Dr. David Vining. Again, he is, I guess the guru of virtual colonoscopy. Tell us, first of all, about, kind of the genesis of VC and, you know, how we got to where we are today.
Well, I’m actually the guy that invented this technology back in 1993 when I was at Wake Forest University, and I was playing video games at home and working with one of the very first spiral CTs in the US. And I had the crazy idea of flying inside the human body. So I was able to write some software that would take the CAT scan data, sort of like slices of the bread and put them together and literally fly inside like a video game. And so, from that I was able to come up with the technology that allows me to look for early colon polyps in cancers.
Explain how that works. So, it’s very; it’s quite non-invasive.
It’s minimally invasive. The common theme between virtual colonoscopy and the real thing is that they both require a bowel prep. You have to take laxatives to get rid of the poop, and then what we do in virtual colonoscopy, is we put a small tube in a patient’s rectum, we inflate the colon with gas, either room air or carbon dioxide. Then, we do the CAT scan and with our modern scanners today, it takes about ten seconds to scan a patient. After which, they get off the table, they go home. Then we, as radiologists we process that data using some three-dimensional imaging and virtual reality computer technology, and we literally fly inside the human body, looking for these colon polyps.
Of course with traditional colonoscopy, you actually have a camera that’s actually, so you’re actually looking at the colon itself. How do problems or issue inside the colon show up on a CT scan?
We’re simply looking for the lumps and bumps inside the colon wall. I guess a point that I like to make is that everyone needs colon cancer screening, not everyone needs colonoscopy. The colonoscopist or the endoscopist often say, well, if we find something with virtual colonoscopy you’re going to require colonoscopy to have that thing biopsied or removed. That’s partly true, except, about ninety percent of the population out there has a normal colon, so if we’re doing colonoscopy on everyone, nine out of ten undergo colonoscopy with this inherent risk of sedation and potential for bowel perforation, unnecessarily. Whereas, with virtual colonoscopy if we can identify that ten percent that requires more invasive procedures, like colonoscopy, that’s where I think we’ll have the greatest benefit. Another added benefit, also a blessing and a curse, depending on how you look at it. With colonoscopy, they only see inside the colon but with virtual colonoscopy we see things outside the colon, including the liver, the kidneys, the pancreas, and other parts of the body, and so there is that chance we’ll pick up disease, early disease that might be treatable outside the colon. The curse is that some of those things that we might see outside the colon turn out to be benign and so, I think in the future, we have to come up with better practice guidelines on what we work up, how we work them up most efficiently and cost effectively.
How is virtual colo, is it colonography, is that exactly what it’s being called? Or…
Well the two terms that are used today are virtual colonoscopy or the other one that’s commonly used is CT colonography, or CTC. So, it’s a matter of to-MAY-to or to-MAH-to.
How is it going in the medical field as far as using VC or, or CT colonography?
Well it’s evolved quite a long ways since I first created it back in 1993. Over the last sixteen years we’ve seen a lot of evolution in the technology and the technique. Early studies back in the early 90’s were not very good. I mean we were still missing quite a few lesions but, in the last couple of years a couple of major multi-institutional clinical trials. In fact, one that included M. D. Anderson just a few years ago, has shown that virtual colonoscopy has ninety percent accuracy for picking up patients with polyps over a centimeter in size; those significant lesions. We had a major milestone a year ago, in March of 2008, when, for the first time ever at the American Cancer Society, finally included virtual colonoscopy as a recommended screening guideline. So that was a major hurdle. The thing that we still face is insurance coverage. Although the American Cancer Society and other national organizations now endorse virtual colonoscopy as being an acceptable screening technology, getting insurance carriers to cover it is our next major hurdle.
I’m assuming they’re probably not a lot of hospitals or centers that are even setup, or have the proper training to do VC right now?
That is true! I think that will change though once the insurance reimbursement shows up. There are many training programs that are being created around the country; in fact, we’re planning on establishing such training programs here at M. D. Anderson. But, unlike the training necessarily required for colonoscopy where you have to have a live patient to pass a scope to learn; with virtual colonoscopy, we can actually train radiologists using already scanned patient data. So, we have these huge databases of past patients to examine and train with.
We’ve heard some of the advantages of VC, in that it’s minimally invasive. What are some of the disadvantages that you have yet to work out?
Well, there are three major disadvantages that are being raised by some of the insurance carriers regarding this technology. One is the radiation dose. I mean, if you were to take a standard CAT scan procedure, the radiation is relatively high, on the order of a hundred to two hundred fifty times that of a standard chest X-ray. But, many of us now practicing virtual colonoscopy are using ultra-low dose techniques so that the radiation risk is only about a hundred times more than a chest x-ray, which is still relatively small and much less than, say, you lived in Denver for a year; where there’s a higher radiation dose to people living in higher elevations. The second major criticism of virtual colonoscopy is its ability to detect lesions outside the colon; these extra colonic findings, and what costs may be incurred are sometimes even unnecessary work ups on benign entities; so I think down the road we need to have better practice guidelines. The third criticism that’s been hurled against it is the training and the generalizability that places like M. D. Anderson where we’re experts in performing the same may not be true out in West, Texas. But, I think the same argument can be made towards colonoscopy, where some of the better results are done by professionals where they do quite a few of these in major medical centers and results are not quite so good out in the rural areas.
When it comes down to these two screening methods, and either one of you can answer this, is it the patient’s choice or is it the doctor’s choice as to who gets which procedure? Dr. Chang?
I think in large part this is a decision that can be made in conjunction between the patient and the doctor. A patient may desire one test or the other but if the particular expertise is not available in the area that should not be a deterrent to being screened. Whatever modality is available, with expertise, should be utilized. There are significant differences as Dr. Vining has already mentioned in terms of the skill of the examiner and that does apply either to colonoscopy or virtual colonoscopy. So, I think that should be a major part of the consideration. But, really, cannot take away from the underlying message, which really ought to be, one way or another, screening should be performed.
We’ve got two different screening methods that we do offer here at M. D. Anderson, and both of them seem to be fairly equal in their outcomes, and so forth. Dr. Chang, do you have any final thoughts, I mean, you did say that screening is very important, but what are your final thoughts?
I would say that this is an opportune time to discuss this topic as we have just completed Colon Cancer Awareness Month. March, every year, is Colon Cancer Awareness Month and I think what, really the message that, that I would like to have delivered, is that don’t be afraid to be screened; don’t be discouraged about any of the preparation that may be required to be screened because screening can save lives. Whether the screening is performed by colonoscopy, or by virtual colonoscopy, or any of the other screening modalities. The important message is, do get screened, and do get screened at regular intervals.
Dr. Vining, we’re so glad to have you here at M. D. Anderson. I guess we stole you away from Wake Forest and it’s our gain and we’re glad to have you here and I hope that you have some, you know, your program grows. What are your final thoughts on virtual colonoscopy and colon cancer in general?
I agree with Dr. Chang. I think everyone needs to be aware of the potential for screening and the various modalities that exist. However, someone at age 50 undergoes screening, I think they need to do it. There will always be newer technologies; I look forward to the day that there’s a new technology that perhaps replaces both colonoscopy as well as virtual colonoscopy. But, the underlying message is that colon cancer is real, it exists, and that no one should have to die from this disease.
Great! Gentlemen, thank you both very much for joining us today! If you have questions about anything you’ve heard today, on Cancer Newsline, contact askMDAnderson at 1-877-MDA-6789 or online at www.mdanderson.org/ask. Thank you for listening to this episode of Cancer Newsline, tune in next week for the next podcast in our series.
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