BILL Casarella awoke in the recovery room after a 5-hour operation with excruciating pain in his chest and his body riddled with tubes and catheters. A few weeks earlier, a scan had revealed nodules in his lungs. When further tests proved inconclusive, Casarella, a 65-year-old radiologist from Atlanta, Georgia, had undergone surgery to remove the lumps.
The news from the lab was good: the nodules were not cancerous, merely the result of a relatively harmless fungal infection. What Casarella had not anticipated was the toll surgery would take. “The tubes were slowly removed, but the excruciating pain lingered,” he wrote in a heartfelt letter to the journal Radiology shortly after his experience (vol 224, p 927). “Two weeks at home taking prescribed narcotics were required before the pain became bearable and a modicum of strength returned.” The irony is that before his annual check-up, Casarella had been fit and well.
Casarella’s experience was the result of a health craze that started in the US a few years ago and has now reached Europe and Australia: CT or computed tomography screening. A CT scan involves sweeping a patient’s body with a powerful beam of X-rays, which are picked up by an array of detectors and then assimilated by a computer to create richly detailed images of up to 64 cross sections or “slices” through the body. A growing number of private clinics tout CT scanning as a way to pick up serious health problems such as tumours, heart disease or weakened bones before symptoms develop – while there is still time to take preventive action.
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According to the HealthTest Scan Center in Boca Raton, Florida, a single CT scan of the chest, abdomen and pelvis – known as whole-body CT – is “the one-minute scan that could save your life”. At around £1000 in the UK, a CT scan like this doesn’t come cheap, but according to the marketing spiel it is the best investment you could ever make.
Some doctors are sceptical, though. At best, CT scans are the ultimate indulgence for the worried well, they say. At worst, they could do more harm than good. CT screening has a relatively high rate of “false positives” – results that appear to indicate a problem where there isn’t one. False positives mean needless worry, potentially harmful investigations and even surgery, as Bill Casarella can testify. Even worse, a recent study suggested that exposing people to the radiation of full-body CT scans could itself trigger cancer. But these concerns seldom get any mention in the scanning clinics’ advertisements. “All medical procedures involve a certain balance of risks and benefits,” says David Brenner, a radiologist at Columbia University in New York, who carried out the radiation research. “The concern I have is that there are clearly some risks – and benefits have yet to be established.”
“False positives mean needless worry, potentially harmful investigations and even surgery”
X-rays have been used to peer inside the human body for more than a century, although CT scanning has only been around since 1972. At first it took hours to do the scans and days to produce the images, but now a scan takes minutes and the pictures are generated almost instantaneously. The patient simply lies on a motorised table as it glides through a ring of X-ray detectors. After processing the images, the computer can even take doctors on a virtual “fly-through” of the patient’s insides.
CT is now well established as a diagnostic tool to investigate patients’ symptoms or monitor the progress of a disease. But in 2000, US clinics began to offer CT scans as a way to screen symptomless, apparently healthy patients. The scans are advertised as a revolution in healthcare. And on the face of it the reasoning is compelling. If a patient gets the all-clear, they can go home reassured. On the other hand, if the scan detects early signs of disease, intervention is possible. For example, if arterial plaques are seen, the patient can switch to a healthier lifestyle and take cholesterol-lowering drugs. If a tumour is spotted, the earlier it is removed, the better a patient’s chances usually are.
Hundreds of scanning centres have opened across the US, to gushing endorsements from celebrities such as Whoopi Goldberg and William Shatner. The technology even featured on the Oprah Winfrey show. Now centres have started opening in the UK and Australia.
It is clearly a lucrative business. The medical justification is less obvious. It is well established in medicine that just because a test for a certain disease exists, it does not necessarily mean that everyone will benefit from it. The damage done by screening lots of symptomless people may well outweigh the benefits (żěè¶ĚĘÓƵ, 22 June 2002, p 34). “If in the process of diagnosing cancer early you actually end up operating on lots of people who don’t have cancer, you are not doing more good than harm,” says Peter Armstrong, a chest screening specialist at St Bartholomew’s Hospital in London.
“We can expect consumers to be intelligent and savvy, but only if they have accurate information”
The only way to find out whether the benefits of screening justify the risks is to carry out a large randomised controlled trial to compare a screened group with a control group. None has so far been done. Citing this lack of hard evidence, the US Food and Drug Administration issued a statement in 2002 pointing out it had never approved the technology for screening purposes.
Proponents of CT screening argue that randomised controlled trials for technologies like this are an expensive waste of time. “They are prohibitively expensive, they take a long time to do and the technology has changed by the time they’re published,” says John Giles, clinical director of LifeScan, a CT screening company with five clinics in the UK.
Another kind of study has suggested that the health benefits of CT screening are negligible, however. Scott Gazelle and colleagues at Harvard Medical School plugged all the data on the technique into a theoretical model of its effectiveness (Radiology, vol 234, p 415). They worked out that after a single full-body CT scan, 90 per cent of patients would require some kind of follow-up, but only 2 per cent would actually have a serious disease. They calculated that, on average, having the scan would increase life expectancy by a paltry six days. They also worked out that this came at a mind-boggling cost of $151,000 per extra year of life gained. This is more than most of the healthcare interventions funded by US insurers. Kidney dialysis, for example, costs up to $80,000 per year of life gained. “I think it is irresponsible to market scans that have no proof of benefit,” says Gazelle.
Advocates of CT screening dispute Gazelle’s assumptions, in particular the number of patients who require follow-up. For example, Larry Gibbons, medical director of the Cooper Clinic in Dallas, Texas, says only 30 to 40 per cent of his patients are referred for further scans or tests. Figures for the industry as a whole are hard to come by. But according to a recent editorial in Radiology, anecdotal comments from screening centres suggest that follow-up rates range from 20 to more than 90 per cent (vol 228, p 26).
While these arguments have yet to be resolved, a study published in September 2004 suggested that full-body CT scanning could actually trigger tumours. It has long been known that a conventional X-ray scan is likely to damage DNA and expose the patient to a very small but measurable risk of cancer. For people who need an X-ray to investigate symptoms, the benefits vastly outweigh the risks. But a whole-body CT scan involves a dose of radiation roughly 100 times greater than, for instance, a breast X-ray. In the latest study, led by David Brenner from Columbia University in New York, researchers calculated that if a 45-year-old man had a full-body CT every year until he was 75, the radiation would increase his risk of dying from cancer by 2 per cent (Radiology, vol 232, p 735). “As risks go, 2 per cent is quite big,” says Brenner.
Again, though, these figures are disputed. Supporters of CT screening point out that long-haul flights, working in a hospital radiology department or even living at high altitude expose people to similar doses. “The amount of radiation you get from a scan is the same as you would get by living in Denver, Colorado, for a year,” says Gibbons. LifeScan’s website equates it to spending six months in Cornwall, where levels of radon gas are notoriously high.
Gibbons agrees that annual full-body scans are not a good idea. “The amount of radiation is a concern and people shouldn’t have one of these every year,” says Gibbons. But several other clinics will perform scans this often, such as Radiology Regional Center – a chain of clinics in Florida – and Lifetest Imaging Center of Nashville, Tennessee.
Some firms that use a modified form of CT scan, known as electron-beam CT, claim that this exposes the patient to a lower radiation dose. But the main factors affecting the radiation dose are the voltage used and the number of “slices” through the body that are taken, says Banner. “These have a far bigger influence on the dose.”
Despite the pitfalls, there are some types of CT screening that are being considered by the mainstream medical community. Just as older women are encouraged to have mammograms, CT scanning of particular organs in patients at high risk of certain diseases might be reasonable. Research published in the Journal of the American Medical Association last year, for example, showed that using CT to screen coronary arteries for the build-up of calcium deposits can provide an early warning of heart disease in high-risk patients, before symptoms appear (vol 291, p 210). A large US study is under way to compare the benefits of using conventional X-rays or CT to screen smokers for lung cancer. And CT scanning of the colon for those at high risk of this cancer has earned tentative approval from the UK’s National Institute for Clinical Excellence.
The diagnostic accuracy of a targeted scan can be improved in various ways. Patients having a scan of their lungs or abdomen, for example, may be injected with a dye that improves the image resolution. Before a colon scan, patients fast and take a laxative, then their colon is pumped full of carbon dioxide.
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But even doctors who support such screening techniques are at pains to point out that their worth has yet to be proven beyond doubt and they are only intended for people in high-risk groups. No one knows if the benefits outweigh the risks for the general population. The medical profession has deep concerns about people going to private clinics after reading a persuasive advert.
Adverts for CT scanning clinics have drawn a lot of flak. A study published last December by Judy Illes of the Stanford Center for Biomedical Ethics showed they often fail to give patients balanced information or refer them to an independent source of advice such as their doctor. Some 30 per cent of adverts made claims that weren’t supported by any scientific evidence (Archives of Internal Medicine, vol 164, p 2415). Many also played on people’s fears. A website for a CT scanning clinic found by Illes’s team features a video sequence shot in a graveyard.
Illes is calling for professional guidelines to rein in such clinics. “These services have fallen through regulatory gaps in this country,” she says. “We can expect consumers to be intelligent and savvy, but they can only be as savvy as the information conveyed to them.” Illes also wants the industry to agree criteria for accepting patients for scans, such as age and other risk factors, and agree how often patients should be scanned.
Gazelle says if anyone is going to produce guidelines for the CT screening industry, it should be an independent organisation such as the US Preventive Services Task Force, a government-funded health advice body based in Rockville, Maryland. “These are the appropriate agencies to be making screening recommendations, not the people who are trying to profit from it,” he says.
The increasing trend for people to take their health into their own hands may seem liberating, but at what cost? Critics point out that while patients pay for the screens out of their own pockets, it is state health providers or insurance companies who have to pick up the tab for costly and perhaps unnecessary follow-ups. The only way to prove that screening is cost-effective is through large, controlled trials. They may cost millions of pounds and take years to complete, but if Gazelle’s study is anything to go by, they could save much more money in the long run.
Whether or not the fashion for CT screening will continue to grow is hard to predict. A recent article on the front page of The New York Times claimed that the “gold rush” was over, because some high-profile private firms had recently gone out of business (23 January). But Gazelle disagrees: “More and more mainline radiology practices are offering whole-body CT screening,” he says. “There’s actually more of it going on now.”
Despite the controversies, some people’s faith in the benefits of CT scanning seems unshakeable. The technique may be unsupported by randomised controlled trials but the promise of cheating death can be hard to resist. Even after his agonising experience, Bill Casarella, who works at Emory Healthcare in Atlanta, Georgia – which offers CT screening services – is still an ardent supporter of screens targeted at particular organs. “I remain in good health,” he tells żěè¶ĚĘÓƵ, “and have scheduled another scan.”
