The case for Virtual Colonoscopy
A report from the latest NEJM is making the rounds:
http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Virtual_Colonoscopy_May_Work_As_Screening_Method_For_Colon_Cancer.asp
"Virtual Colonoscopy May Work As Screening Method For Colon Cancer"
Regular colonoscopies are arguable better for screening (jury is still out). And they are certainly cheaper. The "virtual" version still requires the less than comfortable bowel prep, but NO fiberoptic scope! Think about all the colon cancer we're catching early by using virtual colonoscopy on all those that would otherwise not get colonoscopy screening. (Think of the economic boon for the whole-body scanner operators.) I figure I can get a virtual colonoscopy and a PreGen DNA test (http://www.exactsciences.com) and feel just as assured I will not develop colon cancer in the next 24 months as if I had had a colonoscopy and maybe a guaiac, but for maybe more than triple the cost.
Hey, while you're looking at my DNA, work me up for my genetic risks for heart disease, prostate cancer, hypertension, Alzheimers, alcoholism, and balding. How much extra is that going to cost?
Then there's that capsule endoscopy...
....outside comment:
I can't help commenting on this. The article and commentary in the NEJM failed to mention the radiation involved in virtual colonoscopy. There is a theory out there that small doses of radiation may cause damage that is repaired more slowly than large doses, and the old recommendation stands: avoid unnecessary radiation. I wrote a letter to the NEJM about this, but they probably will ignore me.
My reply:
There is a huge argument over the risks/benefits of virtual versus traditional colonoscopy. Talk to the scanner operators and they'll list any big or small risks of a scope that are negated "virtually" (bowel perforation, bleeding, whatever.) I'm wondering if because there is money to be made, much will be spent on the "can we afford to ignore a test that can save a life?" argument. We'll all want to believe thousands will go undiagnosed unless we support the option of a less invasive screening test. The risk of late diagnosis of colon cancer may be death, an extra bit of radiation presents a much smaller risk, doesn't it?
The studies show the the "virtual" method doesn't pick out the lesions less than 6 mm in diameter as well as colonoscopy, but is better at catching those that approach 10 mm. This has been presented as both an argument for and against the virtual method, and hints to the argument as to whether a more automated analysis via virtual method is better overall than that of a more manual method (subject to clinician skill, experience, etc.)
Some have suggested a form of the "false positives" argument that often gets thrown at the whole-body scanners. That is, if a whole body scan found a splotch in the middle of my kidney, there is no way to know what that splotch means clinically. Thousands of people could be living a hundred years with splotches unbeknownst to them. Or the splotch may be or may become a malignant tumor. There is no way to know clinically, but because I now know it's there I have to suffer through potentially very risky procedures to try and figure out the splotch - even though I have no symptoms, and am not sick. In the case of virtual colonoscopy, can the machine truly identify those that are on their way to colon cancer? Or, is it identifying a population for treatment beyond that which would be found by traditional colonoscopy, but who really aren't at greater risk for colon cancer? On the other hand, will the virtual method miss those that may be at higher risk that may otherwise have been found using traditional colonoscopy?
These arguments will likely pale in the face of "we must support a test that can potentially save a life." The battle over virtual colonoscopies may have been lost when the NEJM said "maybe" they are a good idea.
http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Virtual_Colonoscopy_May_Work_As_Screening_Method_For_Colon_Cancer.asp
"Virtual Colonoscopy May Work As Screening Method For Colon Cancer"
Regular colonoscopies are arguable better for screening (jury is still out). And they are certainly cheaper. The "virtual" version still requires the less than comfortable bowel prep, but NO fiberoptic scope! Think about all the colon cancer we're catching early by using virtual colonoscopy on all those that would otherwise not get colonoscopy screening. (Think of the economic boon for the whole-body scanner operators.) I figure I can get a virtual colonoscopy and a PreGen DNA test (http://www.exactsciences.com) and feel just as assured I will not develop colon cancer in the next 24 months as if I had had a colonoscopy and maybe a guaiac, but for maybe more than triple the cost.
Hey, while you're looking at my DNA, work me up for my genetic risks for heart disease, prostate cancer, hypertension, Alzheimers, alcoholism, and balding. How much extra is that going to cost?
Then there's that capsule endoscopy...
....outside comment:
I can't help commenting on this. The article and commentary in the NEJM failed to mention the radiation involved in virtual colonoscopy. There is a theory out there that small doses of radiation may cause damage that is repaired more slowly than large doses, and the old recommendation stands: avoid unnecessary radiation. I wrote a letter to the NEJM about this, but they probably will ignore me.
My reply:
There is a huge argument over the risks/benefits of virtual versus traditional colonoscopy. Talk to the scanner operators and they'll list any big or small risks of a scope that are negated "virtually" (bowel perforation, bleeding, whatever.) I'm wondering if because there is money to be made, much will be spent on the "can we afford to ignore a test that can save a life?" argument. We'll all want to believe thousands will go undiagnosed unless we support the option of a less invasive screening test. The risk of late diagnosis of colon cancer may be death, an extra bit of radiation presents a much smaller risk, doesn't it?
The studies show the the "virtual" method doesn't pick out the lesions less than 6 mm in diameter as well as colonoscopy, but is better at catching those that approach 10 mm. This has been presented as both an argument for and against the virtual method, and hints to the argument as to whether a more automated analysis via virtual method is better overall than that of a more manual method (subject to clinician skill, experience, etc.)
Some have suggested a form of the "false positives" argument that often gets thrown at the whole-body scanners. That is, if a whole body scan found a splotch in the middle of my kidney, there is no way to know what that splotch means clinically. Thousands of people could be living a hundred years with splotches unbeknownst to them. Or the splotch may be or may become a malignant tumor. There is no way to know clinically, but because I now know it's there I have to suffer through potentially very risky procedures to try and figure out the splotch - even though I have no symptoms, and am not sick. In the case of virtual colonoscopy, can the machine truly identify those that are on their way to colon cancer? Or, is it identifying a population for treatment beyond that which would be found by traditional colonoscopy, but who really aren't at greater risk for colon cancer? On the other hand, will the virtual method miss those that may be at higher risk that may otherwise have been found using traditional colonoscopy?
These arguments will likely pale in the face of "we must support a test that can potentially save a life." The battle over virtual colonoscopies may have been lost when the NEJM said "maybe" they are a good idea.
posted by nawledge at
6:58 PM
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