CAT scan cancer fear; Radiation 'could trigger the disease
in one in 80 patients'.
http://www.dailymail.co.uk/health/article-1235901/CAT-scan-cancer-fear-Radiation-trigger-disease-80-patients.html
Byline: Jenny Hope Medical Correspondent
HAVING a CT - or CAT - scan puts patients at far greater risk of developing
cancer than previously thought, scientists claim.
The radiation generated by the scans - an increasingly popular diagnostic tool -
may trigger the disease in as many as one in 80 patients.
This is far higher than the often used figure of one in 1,000 - with women at
particular risk as they are more sensitive to the effects of radiation.
Researchers now believe the dose of radiation delivered by a CT scan can vary
wildly according to where on the body it is used. In some cases, they suggest, a
single scan can be the equivalent of 442 chest X-rays.
Although the scans - CT stands for computed tomography can be lifesaving in
detecting disease or brain damage, the new U.S. study will heighten fears the
'worried well' paying for them privately could be suf-fering unnecessary harm.
If the American findings were applied to the UK, it could mean CT procedures are
causing thousands more cancer cases than previously thought.
Unlike an MRI scan - which uses magnetic fieldsmagnetic fields,
and radio waves and has no known harmful effects - a CT scan generates
ionising radiation so each dose causes a slight increase in the lifetime risk of
cancer.
The scans allow doctors to build detailed 3D images of internal organs, blood
vessels, bones or tumours.
They were already known to carry a greater risk than ordinary X-rays, such as
those used for breast screening, but the latest research suggests a bigger
problem.
It found the dose of radiation received was larger than thought, although this
varied according to the part of the body being scanned and the age and sex of
the patient.
The researchers concluded there was an average 13-fold variation between the
highest and lowest doses experienced by patients, says a report in the journal
Archives Of Internal MedicineThe Archives of Internal Medicine is a bi-monthly
international peer-reviewed professional medical journal published by the
American Medical Association. Archives of Internal Medicine
University of California Professor Rebecca Smith-Bindman, who led the study,
said: 'The risk associated with obtaining a CT is routinely quoted as around one
in 1,000 patients who undergo CT will get cancer.
'In our study, the risk of getting cancer in certain groups of patients for
certain kinds of scans was as high as one in 80.' The typical dose delivered by
a single CT scan was the equivalent of 74 mammograms or 442 chest X-rays, the
professor said.
Researchers reviewed 1,119 patients in San Francisco who had been scanned in
three body areas - the head and neck, the chest, and the abdomen and pelvis.
The scientists then worked out the radiation dosage of each scan and estimated
the associated lifetime risk of cancer.
A heart examination might involve three scans, looking at different phases of
the pumping cycle. Prof Smith-Bindman said: 'This increases the information that
we can get from the CT procedure, but increases the radiation dose by a factor
of three.' She said doctors need to reduce unnecessary use of scans.
In the UK, the Committee on Medical Aspects of Radiation in the Environment does
not recommend whole body CT scanning for healthy people because the risks
outweigh the benefits. It advises against CT scans for spinal conditions,
osteoporosis and assessing body fat as there are better tests that do not rely
on radiation.