Total Body CT Scanning: A Way to Look for Disease?
At 58 years old, Bill Z worried he was running on borrowed time. His father died of early heart disease. His mother died of cancer. Although Bill felt well, he wondered if his body harbored a killer that could sprout at any time. He'd read about ]]>computed tomography (CT) scans]]> that screen your whole body for disease and he wondered, "Does it really work?"
Like most things in medicine, the answer to Bill's question is yes and no.
What Can a CT Scan Tell You?
A CT scan machine uses x-rays to produce three-dimensional computer images of the heart, lungs, intestines, and other vital organs inside the body. From these pictures, a doctor can find a tumor or other irregularity. In fact, doctors commonly use CT scans to look for suspected problems in a sick person. But using CT scans to screen for abnormalities in a healthy person involves a much more complicated balance of both potential benefit and harm.
Research suggests much promise for the use of CT scans to screen specific body areas—such as the colon, lungs, and heart—for disease when there are medical indications. Amin Chaoui, MD, a radiologist at Boston University School of Medicine says, "Screening for ]]>colonic polyps]]> is a very good test. It has proven to be very effective."
Likewise, studies show that screening specifically for calcium around the heart can identify some people who may be at increased risk of having a ]]>heart attack]]> in the future. On the other hand, although scans of the lungs can effectively find tumors, physicians don't know yet if this early detection saves lives. Some tumors may grow so fast that only very frequent CT scanning (too expensive and with too much radiation) could detect them. Others may have already metastasized dangerously by the time a CT scan can detect them.
What About Total Body Scanning?
Questions arise among the experts when CTs are used in a scattershot way to scan the whole body for disease rather than specific areas. Paolo Raggi, MD, a cardiologist at Tulane University School of Medicine, believes that CT scanning is valuable in looking for ]]>heart disease]]> in someone without symptoms, but worries about whole body scanning.
"I am not against finding things so you can approach it, but what if you find a lot of unnecessary [things]?" he asks. "What are we going to do with it?"
Doctors have even created a new term, “incidentalomas” for tumors–often benign–that are found “incidentally” by regional or whole body CT scanning. These incidentalomas may be found in the thyroid, parathyroid, kidneys, adrenals, liver, kidneys, or brain. Finding an incidentaloma can lead to further testing or even surgery, and is more likely to lead to ]]>anxiety]]> and cost than improved health outcome or saving of life.
What Dr. Raggi and others worry about is whether performing CTs in normal people will generate a high number of false positives and false negatives. False positives occur when a scan of a healthy person's body finds something that looks suspicious for disease (such as an incidentaloma) but turns out on further exploration to be benign. This outcome can generate needless worry and cause side effects from other tests now needed to "rule out" a problem.
False negatives occur when something appears normal at the time of the test, but the person actually has a disease that will manifest in the near future. In other words, the test fails to pick up the disease and the person is "falsely reassured." Experts argue that currently there is just not enough experience with total body scanning in normal people to know if the false positive and false negative rate is low enough for this to be a good test.
Other physicians argue that since we have the technology of the CT scan, why not use it. Max Rosen, MD, associate professor of radiology at Harvard Medical School says, "The best uses [of total body CT scan screening] are to give patients intelligent information about their health status that they can use to make decisions about future medical care or lifestyle choices." He feels as long as the risks and benefits are clearly discussed, total body CT scan screening can only add to the overall knowledge of a person's health.
Dr. Rosen also dispels the severity of the radiation risk saying that the radiation exposure from most CT machines is equal to the radiation you receive from riding across the country on an airplane. The US Food and Drug Administration is very cautious in its assessment of the radiation risk from full body CT scanning:
The principal risk associated with the radiation dose to a person from a CT procedure is the small possibility of developing a radiation-induced cancer some time later in that person's life. For a patient with a medical need, the benefit of a diagnostic or therapeutic CT procedure recommended by a physician normally far exceeds the small cancer risk associated with a CT procedure. The FDA, in its 2005 statement on whole body CT scanning is much less cautious in its assessment of benefits from this procedure: “Any … presumed benefit of whole-body CT screening is currently uncertain, and such benefit may not be great enough to offset the potential harms such screening could cause.”
For a person without symptoms, CT screening is unlikely to discover serious disease, and the potential harm to the individual may be greater than the presumed benefit. There is no data demonstrating that whole body CT screening of individuals without symptoms provides a greater probability of benefit than harm. One small study has shown significant disagreement between radiologists in reporting the results of whole body scans and found no difference in two year mortality between a group of persons given a scan and a second group not scanned. The one major difference between the two groups was in the costs of medical care after the scans: these were twice as high for the screened group as for the non-secreened persons. The authors used this study to argue that a study which could definitively determine if scanning is beneficial would be both difficult and very expensive. A 2005 study on 1200 scanned persons found that the average number of abnormal findings per person was nearly 3, and that 37% of individuals scanned received a recommendation for further studies of some kind. It was unclear which if any of these findings led to health benefits.
The exception to this fairly pessimistic view is “CT virtual colonography”. This is a technique in which CT scanning is used to screen asymptomatic individuals for polyps that might someday lead to colon cancer. While there is still more to learn about the role that this type of scanning can play, current evidence suggests that its benefits likely strongly outweigh any risks.
Still a New Concept
Currently many radiologic centers offer total body CT scans. The cost for a total body CT scan ranges from $300-$1,200, depending on where it's done. The cost is not covered by health insurance, and referral from a primary care physician is often not required.
Also, since total body scanning is new, no one knows how often it should be done. For someone with risk factors like a family history of heart disease, repeated screenings over time may be helpful, but again the answer is unknown.
As for Bill Z, he decided to try it. He had a CT scan to look for calcium in his heart vessels. The results showed calcium and some masses in the liver. After further tests, the liver masses turned out to be okay, but the calcium suggests he is at significant risk for heart disease. Still, he's happy he had the test.
"The results helped tip the scales for me to lose weight and get my blood pressure down," he says.
American Academy of Family Physicians
US Food and Drug Administration
Ontario Association of Radiologists
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Furtado CD, Aguirre DA, Sirlin CB, Dang D, Stamato SK, Lee P, Sani F, Brown MA, Levin DL, Casola G. Whole-body CT screening: spectrum of findings and recommendations in 1192 patients. Radiology . 2005 Nov;237(2):385-94. Epub 2005 Sep 16.
Obuchowski NA, Holden D, Modic MT, Cheah G, Fu AZ, Brant-Zawadzki M, Seballos R, Mohammed TL. Total-body screening: preliminary results of a pilot randomized controlled trial. J Am Coll Radiol . 2007 Sep;4(9):604-11.
Last reviewed July 2008 by ]]>Lawrence Frisch, MD, MPH]]>
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