Medicare: CT Colonography Not Ready For Primetime

On February 11, Medicare released a preliminary statement on coverage for CT colonography in colorectal cancer screening. The verdict: CT Colonography should not be covered by Medicare. CT Colonography or 'virtual colonoscopy' is a technique to detect cancerous and pre-cancerous lesions of the colon that uses a 3D reconstruction of the colon to create a virtual flythrough and guide further, more invasive, investigations.

The Decision Memo is preliminary, and Medicare canvassed for comments:

"We are requesting public comments on this proposed determination pursuant to Section 1862(l) of the Social Security Act. After considering the public comments, we will make a final determination and issue a final decision memorandum. As with all national coverage analyses, the public may submit comments or additional evidence that cause us to reassess our evidentiary review and arrive at different conclusions. If that should occur during finalization of this decision memorandum and we determine that CT colonography is clinically effective, then we would need to determine, using current or additional cost information, if CT colonography is cost effective. We are asking for public comment on the cost effectiveness of screening CT colonography for the Medicare population if we were to alter our clinical decision."

It's not clear to me if that means Medicare has already determined that CTC is clinically effective but are awaiting evidence of cost-effectiveness or what.

A discussion of the test's accuracy can be found at the New England Journal of Medicine, where a recent report was published on the ACRIN study 6664, "Computed Tomographic Colonography in Screening Healthy Participants for Colorectal Cancer." The study found that CTC could detect 90%of abnormalities greater than 10 mm (about 3/8") in size compared to a gold standard of colonoscopy.

Dr Robert Fletcher commented on the study findings in the NEJM citing several reasons why he was underwhelmed. He notes that 17% of the subjects were thought to have polyps larger than 10 mm, but only 1 in 4 actually did on confirmation colonoscopy. In 16% of subjects, there were incidental findings outside the colon, and these usually don't amount to anything substantial (aside from life-threatening abdominal aortic aneurysms). On this point he cites his previous editorial in support! He also mentions the inconvenience and discomfort of scheduling a colonoscopy to evaluate abnormal colonic findings on CTC, though more than 80% of patients are spared such an examination by undergoing CT first. He warns of the threat posed by radiation risk, though he concedes that the dose from one such scan "may be acceptable" and the "radiation risk is uncertain." It is perhaps worth noting that Dr Fletcher disclosed his past role as a consultant to Exact Sciences, a company exploring competing technology for colorectal cancer screening, stool-based DNA screening.

If you wish to influence Medicare's decision, you can submit your comments here, I believe. They do take public commentary seriously. In fact, they provide a detailed review of public comments in their Decision Memo. The comments included feedback in support of CTC from the American Cancer Society, American College of Radiology, American Gastroenterological Association, and--perhaps less impressively--from the Medical Device Manufacturers Association and Medical Imaging Technology Alliance. Thirty-four lay public also commented, and the content of their comments are noted in the memo.

To be honest, I'm impressed with the transparency, frankness, comprehensiveness, and quality of the Decision Memo, and agree that the evidence for supporting CTC in the Medicare population, with an average age of 75 years, is weak. Probably worthwhile applying this technology to younger subjects, however. This decision should not be taken to suggest otherwise.