Should you ask your doctor to CT scan you from head to toe?

Answers to your questions about the news.
Nov. 6 2010 7:14 AM

Full-Body Scam

Should you ask your doctor to CT scan you from head to toe?

Medical high-speed CT fully body scanner.
CT body scanner

A recent study showed that current and former heavy smokers can reduce their risk of dying of lung cancer by getting annual chest CT scans. The screening was so beneficial that the monitoring board called a premature end to the research so as to prevent unnecessary deaths in the control group. Smokers are at increased risk for lung cancer, but most adults have at least one cancer risk factor—whether it's family history, excessive sun exposure, or eating too much steak. If regular scanning is so great for smokers, should we all be getting full-body scans?

Definitely not. No study of significant size has shown that preventive, whole-body CT screening extends life. The procedure presents all kinds of problems. For example, it's very hard to see anything in the abdomen and bowel without intravenous or oral contrast fluid, which is rarely used in this context. Even if whole-body scans could reliably detect incipient cancers, doctors suspect the risks of increased radiation and unnecessary follow-up testing would outweigh any potential benefit. The federal government and the American College of Radiology both discourage full-body scans in patients with no symptoms. The FDA even prohibits manufacturers from marketing their machines for use in healthy people.

Of course, many doctors opposed the chest CT scans for smokers until the recent study proved them wrong. But that test was the latest development in more than 10 years' worth of methodical research, including the development of protocols and guidelines for reading the results. The government is unlikely to shell out more than $200 million—the cost of the lung cancer study—until full-body CT scan proponents can show persuasive evidence of a positive effect.

The radiation from a single, whole-body scan may increase your risk of developing cancer by 0.08 percent. Preventive scans also return more false positives than actual problems, because most of your nodules, cysts, and scars probably won't ever hurt you. Full-body scanning centers refer between 20 percent and 90 percent of patients for follow-up exams, depending on the location. But studies suggest that only 1 percent to 3 percent of adults who aren't experiencing symptoms actually have any latent heath problems, which means there's a whole lot of useless screening being done after these whole-body scans. Some of the secondary tests are low-risk, like urine analyses for renal cysts, but others can go very badly. One in every 100 patients experiences serious side effects from the follow-up procedures, like heavy bleeding during liver biopsy.

Even in cases in which the full-body scan uncovers something potentially dangerous, there's little evidence that the information helps. Small tumors are very hard to see in a whole-body scan, and the advantage of catching larger cancers a bit earlier may be negligible: The marginal extra time afforded for treatment would save the patient's life only a fraction of the time.

Then, of course, there's the money. You might be willing to shell out between $800 and $1,300 for your CT scan, but what about follow-up tests? Those additional—and usually unnecessary—examinations can cost tens of thousands of dollars. At present, most insurance companies seem willing to cover those costs, but there might be a fight if elective whole-body CT scans become more popular.

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Explainer thanks Shawn Farley and Ella Kazerooni of the American College of Radiology and Claudia Henschke of Mount Sinai Medical Center.

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Brian Palmer is Slate's chief explainer. He also writes How and Why and Ecologic for the Washington Post. Email him at explainerbrian@gmail.com. Follow him on Twitter.