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    Tuesday, April 28, 2009

    Virtual Colonoscopy [VC]-What I tell my patients.

    Colon cancer is one of the most common and deadliest malignancies. Around 50,000 people die every year from colorectal cancer, mainly because they were not screened. Perhaps screening did not occur because they avoided a traditional optical colonoscopy- medicine's most unloved procedures. Colorectal cancer can be prevented -- or even cured and is highly treatable if detected early, but it remains the nation's second deadliest cancer. For years, the most reliable screening method has been optical colonoscopy, in which an endoscope is used to inspect the walls of the intestine and remove abnormal growths, or polyps.

    In a standard optical colonoscopy, a doctor inserts a long, flexible tube with a tiny camera at its tip into a patient’s rectum and colon. In a virtual colonoscopy, the doctor uses CT scans to produce images of the colon’s interior. If worrisome polyps are spotted, the patient then has to have them removed by a standard colonoscopy. Virtual colonoscopy uses three-dimensional images from a CT scan to detect polyps or cancers in the colon. When detected early the risks of colon cancer death decreases.

    But will Medicare and other insurance carriers pay for it?

    On Feb. 11, 2009, a federal agency -- The Centers for Medicare & Medicaid Services --drew a simple conclusion: "The beneficial evidence is inadequate." It recommended Medicare not cover virtual colonoscopy.

    This decision not to pay for VC has now become a political issue. Over 40 members of Congress urged on by proponents backing the new procedure -- the medical imaging industry, including other supporters, many of them radiologists who read CT scans have signed letters urging federal officials to reconsider. The dispute has even split doctors in the same specialty: the American Gastroenterological Association favors Medicare coverage, while the American College of Gastroenterology does not. VC has also received key endorsements as a first-line screening test from influential medical groups, notably the American Cancer Society, after several large studies found it to be effective at finding large polyps.

    The U.S. Preventive Services Task Force expressed reservations. An independent panel of health experts, concluded that there is insufficient evidence that virtual colonoscopy would benefit Medicare recipients. CMS cited concerns about radiation exposure and the number of patients who would require follow-up colonoscopies to remove polyps, as well as the inability of CT scans to reliably detect small or flat growths. The preventive services task force found that 7 to 16 percent of patients who undergo virtual procedures will have a finding "of potential clinical significance," but the panel said it is not known whether discovery "results in better outcomes for patients; it is possible that they result in extra follow-up testing without associated benefit."

    Disputes over the cost-effectiveness of virtual colonoscopy further complicated the analysis. The procedure, which typically costs less than $1,000, can be half as expensive as a traditional colonoscopy. However, some 20% of patients will have a polyp requiring a follow-up optical colonoscopy to have the growth removed. That has led to criticism that virtual colonoscopy is duplicative.
    Q&A adapted from the ACG

    1. What is VC aka CT colonography?
    CT colonography often referred to as "virtual colonoscopy." It is a CT scan x ray test designed to simulate colonoscopy to look for large colon polyps and cancers. Some patients are thought to prefer CT scans because they are less intrusive.
    Is that true?

    2. What happens during a CT colonography?
    First, a radiology technician inserts a tube into your rectum and gas is pumped into the colon until it is fully expanded. Then you are asked to hold your breath while lying on your back and a CT scan is performed. You then turn over onto your stomach and again hold your breath while a second CT scan of the abdomen and pelvis is performed.

    3. Does it require bowel-cleansing (laxatives)?
    Yes. The bowel-cleansing regimen is the same as that for colonoscopy. On the day before the procedure, you stay on clear liquids all day and on the evening before and the morning of the procedure; laxatives are taken to flush waste from the colon.

    4. Is CT colonography painful?
    Because no sedation is used, the expansion of the colon with gas can be painful. In some studies, patients reported more pain and discomfort with CT colonography than with a colonoscopy. Colonoscopy may be more comfortable because sedatives are given during the examination.

    5. What happens after the test?
    The radiologist will examine the colon and other structures within the pelvis and abdomen and generate a report for the physician who ordered the test. Sometimes information about polyps in the colon is known immediately. If so, some radiology centers and endoscopy units are equipped to perform colonoscopy and remove the polyp on the same day without having to repeat the bowel preparation. If not, colonoscopy will need to be performed on yet another day with the same amount of bowel cleansing discomfort prior to the colonoscopy.

    6. Summarize the advantages of CT colonography.
    • CT colonography is less invasive than colonoscopy.
    • It has a lower risk of perforation of the colon.
    • CT colonography is typically performed without sedation so no separate car driver is needed to drive you home.
    • One of the other benefits of virtual colonoscopy is its ability to detect other cancers and abnormalities -- tumors in the kidney, liver or lungs, and aortic aneurysms -- because of its additional images involving a wider area of the body.

    7. How accurate is CT colonography?
    • According to recent studies, CT colonography is 90% sensitive for the detection of patients with a polyp 1 cm or larger.
    • These large polyps constitute about 10% of all colorectal polyps and are the most likely to develop into cancer.
    • For polyps, less than 1 cm in size, however, the sensitivity of CT colonography falls off rapidly.
    • For polyps 6 to 9 mm in size, the sensitivity of CT colonography is well below 90%.
    • For polyps 5 mm and smaller, which constitute about 80% of all precancerous polyps in the colon, CT colonography is unreliable.
    • Radiologists are currently advised to NOT attempt interpretation of polyps 5 mm and smaller in size. Since some researchers believe there is a subset of small polyps smaller than 5 mm turn into cancer that are aggressive and malignant not being able to report on them is a disadvantage of VC.

    8. How often does the traditional colonoscopy remove polyps?
    The older the patient, the greater the chance that a polyp will be detected that requires a complete colonoscopy. In the hands of the best CT colonographers, about 12% of patients undergoing CT colonography will require colonoscopy and polypectomy, but in older populations, this number increases to 20 to 25%.

    9. Is CT colonography paid for by insurance?
    Currently, CT colonography is usually paid for if a colonoscopy is unable to be completed, or when cancer is detected by colonoscopy and the cancer blocks passage of the colonoscope.
    The Center for Medicare and Medicaid Services reviewed above recently decided to not cover CT colonography for screening for Medicare patients.
    Some private insurers, however, currently cover CT colonography for screening.

    10. How often should CT colonography be repeated?
    • CT colonography is currently recommended at 5-year intervals. If the study is normal,
    • Colonoscopy is recommended at 10-year intervals.
    • The difference in intervals between the two tests is accounted for CT colonography’ s lack of efficacy at detecting small colon polyps, and current uncertainty about how often these polyps will turn into cancer.

    11. What are the risks to CT colonography?
    • The immediate risks of CTC include a small rate of perforation related to gas distension, which is lower than the risk from colonoscopy.
    • Potential long-term risks include missing small polyps that could develop into cancer as mentioned above.
    • In addition, studies have found that multiple CT scans can increase the risk of cancer.
    • The risk from radiation exposure is uncertain.
    • The radiation dose from a CT colonography is equivalent to about 250 chest x-rays.
    • One expert estimated that a 50-year-old patient undergoing CT colonography would have a 1 in 714 chance of developing a solid tumor from radiation. This risk, however, must be balanced against a substantially higher than the risk of perforation from colonoscopy.
    • The US Preventative Services Task Force cited radiation risk as one of the factors underlying their decision to not endorse CT colonography as a colorectal cancer screening test.
    • Another risk pertains to findings seen on CT scan outside the colon, which when of no clinical significance often lead to the significant inconvenience, cost, and risk of additional follow-up x-ray tests to further characterize these incidental findings.
    • CT colonography also produces a considerable number of "false positives.” This means that if a radiologist finds a polyp on CT colonography, there is a less than 50% chance that a polyp is actually present at the colonoscopy.

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