The Centers for Medicare and Medicaid Services said in a decision posted on its website that there was insufficient evidence to conclude that virtual colonoscopy (CT colonography) improves outcomes in Medicare patients. The agency is taking public comments for 30 days before issuing a final decision.

Dr. Sean Tunis, a former chief medical officer for Medicare, said that there had been cases where a tentative coverage determination had been
changed but that this one seemed to be pretty carefully and fully considered.

The United States Preventive Services Task Force, which advises the government on prevention, said last year that there was insufficient evidence to assess the benefits and harms of the CT technique. Some private insurers pay for the tests; others do not.

Medicare also said many studies supporting virtual colonoscopy were conducted in people with a mean age around 58, so results might not apply to Medicare's older population. For instance, older people are more likely to have polyps. So the proportion of people who would have to have a conventional colonoscopy after a virtual one would be greater. That would make the CT scan less cost-effective.

Opposing the Medicare decision, the American Cancer Society last year began recommending virtual colonoscopy as an option for colon cancer screening. According to an article published in the June 1, 2007 issue of CANCER, the society's journal, "targeting smaller (5 mm or less) lesions does little to significantly reduce the incidence of colorectal cancer and, in fact, results in extremely high financial costs and a large proportion of adverse events.

"A cost-benefit analysis study says the low malignancy rate among so-called diminutive polyps gives virtual colonoscopy with removal of lesions 6 mm or greater the best estimated value per life year gained and with fewer complications," the authors write.

"Effective screening through increased use of any of several available tests is the key to reducing deaths from colorectal cancer, the third most common cause of cancer death among both men and women in the United States. Despite the availability of effective screening tests, screening rates remain low and colon cancer deaths remain high."

The report goes on to say that "optical colonoscopy (OC) and flexible sigmoidscopy (FS), have been the primary screening tools for the last few decades but are associated with complications, from abdominal pain to life-threatening bowel perforation and bleeding. Virtual colonoscopy, or CT colonography (CTC), has arisen as a potentially effective CRC screening tool.

"Using x-rays and imaging software to develop two- and three-dimensional images of the gastrointestinal tract, it has fewer adverse effects and is better tolerated by patients. Recent studies using new methods have demonstrated that the test is very sensitive for colon cancer and could be an effective screening option for patients," the study says.

Analyzing the cost/benefit ratio of the two procedures, the CANCER article notes that "previous cost-benefit analysis studies comparing OC and CTC (with OC referral for all polyps of any size) have estimated that OC is more cost effective. However, these studies ignore current CTC guidelines that recommend only reporting polyps greater than 5 mm.

"Dr. Perry Pickhardt, a radiologist from the University of Wisconsin, collaborated with Dr. Cesare Hassan, a gastroenterologist from Rome, and colleagues to conduct a cost-benefit analysis comparing CTC with and without a 6-mm polyp size threshold, OC and FS.

"In this model of 100,000 persons over 50 years old, CTC, or virtual colonoscopy, with OC follow-up of polyps greater than 5 mm was the most cost-effective screening test. According to cost per life-year gained calculations, CTC with a 6-mm threshold for follow-up cost only $4,361 while OC cost $9,180 per life-year gained. CTC with no polyp size threshold cost $7,138, and FS cost $7,407 per life-year gained.

The authors conclude that incremental costs of working-up lesions smaller than 6 mm at CTC resulted in a significant $118,440 per additional life-year gained and accounted for more than half of all OC procedures. Moreover, working up these small, almost always benign polyps with OC, caused considerable complications.

The study found almost half of all OC-related complications were attributable to work-up of diminutive lesions. Furthermore, targeting these lesions did not improve screening efficacy, reducing CRC incidence by only 1.3 percent.

The authors conclude the data support "CTC with nonreporting of diminutive lesions" to be "the most cost-effective and safest screening option available, and that providing additional effective yet distinct screening options like CTC could encourage more adults to undergo screening and consequently increase overall compliance with screening" for CRC.

Opposing this view, gastroenterologists point out that CTC, especially if performed more than once, could expose patients to dangerous levels of radiation.

Sources: Medicare and American Cancer Society

Article: Cost Effectiveness of Colorectal Cancer Screening With Computed Tomography Colonography: The Impact of Not Reporting Diminutive Lesions," Pickhardt PJ, Hassan C, Laghi A, Zullo A, Kim DH, Morini S, CANCER: Published Online: April 23, 2007 (DOI: 10.1002/cncr. 22668); Print Issue Date: June 1, 2007.