In their February 2 piece, internal medicine physician Dr. Samita Garg and gastroenterologist Dr. Dennis Ahnen from the University of Colorado Denver School of Medicine said that CMS and the U.S. Preventive Services Task Force (USPSTF) were inconsistent in their comparison of screening modalities in reports produced last year.
"The rationale against recommending or covering CTC screening includes concerns about radiation exposure, false-negative rates for small polyps, the discovery of extracolonic findings, variability in performance, a lack of targeted studies and a higher adenoma rate in the Medicare-eligible age group, and an absence of evidence that covering CTC would increase overall screening rates," Garg and Ahnen wrote (Annals of Internal Medicine, February 2, 2010, Vol. 152:3, pp. 178-181).
For example, CMS criticized CTC for not detecting diminutive polyps as well as colonoscopy, although the benefit of removing them is unknown. Conventional colonoscopy commonly misses 25% of small polyps and 12% of clinically significant polyps (> 1 cm), while sigmoidoscopy misses even more, and the fecal occult blood test (FOBT) "misses almost all small polyps," Garg and Ahnen wrote. "Nevertheless, these failings have not been raised as major concerns regarding these screening tests."
Radiation is a legitimate concern regarding VC, but the USPSTF traditionally has recommended the barium enema exam, which delivers an equivalent radiation dose. In writing its new guidelines, CMS "did not cite radiation exposure as a major concern," the authors added.
CMS also noted the varying accuracy of CTC by center, while failing to compare other screening modalities. At colonoscopy, for example, detection rates for significant adenomas "vary up to four-fold," the team wrote, and "there is a more than 10-fold variation in colonoscopy complications, with perforations ranging from 0.07% to 0.72%, and postpolypectomy bleeding ranging from 0.2% to 2.67% (21, 22)."
Only a few VC studies have specifically examined Medicare-aged patients, CMS charged. Still, the authors noted that "to our knowledge, targeted studies of the other colorectal cancer screening tests in patients 65 years and older have not been reported."
There are also fears of higher adenoma rates in older patients, which would be counterproductive for VC. However, many older groups have sufficiently low adenoma rates to permit CTC screening. Moreover, the use of flexible sigmoidoscopy in this population could be similarly criticized, Garg and Ahnen wrote.
CTC was criticized for some studies showing reduced cost-effectiveness vis-à-vis colonoscopy; however, this is also the case for FOBT and flexible sigmoidoscopy, a finding that did not prompt a reevaluation of these two modalities.
"Taken together, these points seem to indicate that CTC is being held to a higher standard than the colorectal cancer screening tests that are currently recommended by the USPSTF and covered by the CMS," the authors wrote.
By Eric Barnes
AuntMinnie.com staff writer
February 5, 2010
How 2009 went right and wrong: VC's own worst enemies, October 28, 2009
JACR editorial: Medicare used double standard in VC decision, September 22, 2009
NEJM editorial lauds CMS rejection of VC, May 28, 2009
CMS rejects Medicare coverage for virtual colonoscopy, May 12, 2009
American Cancer Society recognizes virtual colonoscopy screening benefit, March 5, 2008
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