Kendrick asks...what's the point of full body CT scans?
They’re becoming increasingly popular, but is there any clinical justification for people to pay for body scans? Dr Malcolm Kendrick looks at the evidence
They're becoming increasingly popular, but is there any clinical justification for people to pay for body scans? Dr Malcolm Kendrick looks at the evidence
Private CT scans for healthy individuals are becoming increasingly popular despite the hefty price tag of about £1,500. They are advertised in emotive ways. One London-based company presents the benefits thus:
‘For many people, a disorder is only detected when the symptoms have been present for a long time. A preventive examination will enable you to find out in time or just to get some certainty regarding your health. That alone often gives peace of mind.'
This may sound eminently reasonable. But there is not the slightest evidence that a healthy person having a CT scan will enjoy a reduced risk of mortality or morbidity. No controlled trials have shown any benefits – at all. Although CT cardiac scanning can, for example, demonstrate a coronary artery calcification, what can then be done about it that is not already being done?
On the other hand, there are many ways in which using CT scans for screening can do damage. The first is that these scans expose people to a very high dose of radiation, and there is a real danger of causing cancer.
The Committee on Medical Aspects of Radiation in the Environment (COMARE) recently published a report, The impact of personally initiated X-ray computed tomography scanning for the health assessment of asymptomatic individuals.
To quote that report: ‘If 100,000 people undergo a CT scan every five years from age 40 to 70 years, receiving an effective dose of 10mSv from each scan, then the estimated impact is approximately 240 excess fatalities. For scanning at higher frequencies (every two years or annually) this increases to 600 and 1,200 fatalities, respectively. These estimated risks are proportional to dose.'1
If, as is likely, the popularity of these private scans grows, more than one million people are likely to undergo regular CT scans. Were this to happen, the number of cancer deaths directly caused by the scans in the UK would be between 2,500 and 12,000.
It is interesting to compare this with an assessment of the benefit of statins, taken from a press release on the Heart Protection Study trial. ‘In this trial, 10,000 people were on a statin. If now an extra 10 million high-risk people worldwide go onto statin treatment, this would save about 50,000 lives each year – that's 1,000 a week.
These results are at least as important as previous findings for aspirin's effects on heart attack and strokes. Those findings changed medical practice, and we expect these to have the same effect. In fact, statins are the new aspirin.'2
If 10 million people were to have regular CT scans, the number of deaths caused would be between 25,000 and 120,000 – the higher figure is equivalent to the entire population of Runcorn and Widnes. It is hard to imagine that any new drug treatment would be approved if it were to cause such a high number of deaths.
Peace of mind?
Although advertising for CT scans promises ‘peace of mind', this is only true if nothing is found on the scan. It would seem this rarely happens. Few researchers have reported on follow-up of a large number of individuals undergoing whole-body CT, except for a study in California of more than 1,100 individuals at an outpatient imaging centre in Southern California.
The majority had personally initiated the procedure and only 4% had significant medical history. Only 14% had no findings at all, and 11% had six or more findings3. This is not likely to engender peace of mind. It must also be borne in mind that the vast majority of these ‘incidentalomas' do not have any clinical significance2. Yet, many of them require further investigations, more scans and, in some cases, invasive surgery.
False negatives are another problem. These are less common than false positives, but the dangers are clear.
Another major downside, in the UK, is that many clinics offering scans do not follow up on their findings. If something is found, the patient has to visit their GP for further investigation, and the costs are then usually transferred back to the NHS.
Screening healthy people with CT scans is not remotely evidence-based. It holds out the hope of picking up early-stage disease, then being able to cure it. It claims to provide ‘peace of mind'.
The reality is that they increase the risk of cancer, pick up a large number of ‘incidentalomas' that then have to be investigated – at great cost.
Dr Malcolm Kendrick is a GP in ManchesterDr Malcolm Kendrick: there is not the slightest evidence that a healthy person having a CT scan will enjoy a reduced risk of mortality or morbidity Dr Malcolm Kendrick: there is not the slightest evidence that a healthy person having a CT scan will enjoy a reduced risk of mortality or morbidity Healthy people who choose to have regular CT scans increase their cancer risk