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Suppose you eat five a day, go to a gym and take the latest supplements. What else can you do to maximise your chances of a long and healthy life?
Some might say it’s to lie down inside a huge medical imaging machine for an hour or two while it scans your whole body, looking for cancer or any other medical problems that haven’t begun to cause symptoms.
These scans are soaring in popularity, increasingly being advertised with celebrity endorsements and provided by reputable medical companies.
And yet, many doctors are ringing the alarm bell over this health trend.
They say these scans are not backed by research evidence and are likely to do more harm than good, because they find too many “false positives”.
“They are opening Pandora’s box,” said Dr Cindy Chew, a radiologist at the University of Glasgow.
How the scans work
The scans use magnetic resonance imaging (MRI) machines to make thousands of cross-sectional pictures of the inside of the body.
They were developed to investigate people with symptoms suggestive of cancer or other conditions in a particular part of the body. This kind of use is not in question.
But scanning the whole body to find diseases that aren’t causing symptoms is more controversial.
It might sound like a no-brainer. We often hear that the earlier a cancer is found, the easier it is to treat. Some even claim that if people had the scans regularly enough, they could radically cut their risk of ever getting cancer.
But such arguments fail to consider the problem of false positives. These happen when a scan finds some kind of anomaly that eventually turns out to be harmless – something that didn’t require treatment and would have been better left alone.
“We know that healthy, normal people have got small abnormalities in their bodies, most of which will never reach their attention, because they were never going to do any harm,” said Dr Margaret McCartney, a GP and Director of the Centre for Evidence and Values in healthcare at the University of St Andrews. “The problem is, if you show people these abnormalities, there’s a temptation to investigate them further, and that can lead to harms.”
What kind of things are false positives? It could be cyst, a small fluid-filled lump. It could be a benign clump of cells, which is not growing, or is growing so slowly it will never cause harm, and will eventually be destroyed by the immune system.
But an MRI scan cannot distinguish between these harmless lumps and the dangerous growths we call cancer. So, every kind of anomaly found on the scan will trigger a cascade of further tests, scans, biopsies and eventually surgeries to remove the cells.
Do the benefits outweigh the risks?
No medical intervention is without risk – surgeries and even biopsies can cause infections, bleeding and removal of part of an organ.
That’s not to mention the stress, when people are turned from someone who was completely healthy to a potential cancer patient overnight. “You could worry non-stop about it,” said Dr Chew.
So the key question is: Do whole body scans for healthy people find enough real cancers to outweigh the risks from the non-dangerous anomalies?
That can only be known for sure by a randomised trial, where half the participants get whole body scans and half do not. In most countries, screening programmes – like those for breast cancer in women from 50 to 70 – are introduced only when such a trial shows the benefits from finding real and dangerous cancers outweigh the harms from false positives.
Unfortunately, such a study has not been done for whole body scans. But there are hints about the dangers from similar cases.
South Korea brought in thyroid cancer screening using ultrasound scans in 1999, triggering a surge of diagnosis and surgery. But most of the tumours found were tiny nodules that were harmless.
By 2011, the rate of people diagnosed with thyroid cancer in South Korea had risen 15-fold – but the number of people dying from it each year was just the same.
That proves all those extra diagnoses had not saved any lives and the extra surgeries were useless. They also created a huge group of people taking artificial thyroid hormones for the rest of their lives, said Professor Matt Davenport, a radiologist at the University of Michigan and a long-time critic of whole body scans. South Korean medical bodies now advise against thyroid screening.
In a similar example, a US trial of screening for ovarian cancer, using ultrasound scans and a blood test, also failed to help people.
The same number of women were diagnosed with this tumour in both the screened and non-screened groups. In other words, the screening was only picking up cancers that women noticed themselves because of symptoms.
And in the screened group, more than a thousand women had unnecessary surgery for benign anomalies, and a fifth of them had a major complication from the surgery.
As a result, the researchers recommended the US does not introduce ovarian cancer screening.
Because there has been no randomised trial of whole body screening, we can’t know for sure how often there would be false positives. But studies of people having MRIs for recommended reasons suggest a 3 in 10 chance they find some kind of anomaly unrelated to the original reason for the scan.
A new warning
Whole body scans are not recommended by any medical society in the world. In the US, where the approach originated, the American College of Radiology says: “There is no documented evidence that total body screening is effective in prolonging life. In addition… such procedures lead to the identification of numerous non-specific findings that will not ultimately improve patients’ health.”
Even with these concerns, it could be argued that some people may still like to have the scans. If they can afford the price tag of £2,000 to £3,000, then isn’t it up them?
In all other areas of medicine, it is seen as bad practice to offer people interventions without fully informing them of the risks.
Yet the firms advertising the scans, rarely provide information about the risks of false positives.
This month Professor Davenport wrote an article in the medical journal JAMA, calling on firms to give customers a “health warning” about the scans, which would include the following information:
No medical guideline recommends that you undergo this test. There is a 3 in 10 chance we find something that creates uncertainty for you, which could result in anxiety, life disruption, more imaging, invasive procedures, or possibly surgery. Although cancer will be identified in 1 or 2 out of 100 people, finding cancer with this test is unlikely to help you because most types will be low risk or already advanced. If you undergo this test, you are more likely to be harmed than helped.
Despite the resistance from doctors, it’s hard to see the scans going away. But at least such a warning could help make sure people are undergoing them with their eyes wide open.
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