CT scans increase children’s cancer risk

CT scansCT scans increase children’s cancer risk 

Children who are given powerful CT (computed tomography) scan—which delivers high doses of radiation—are more likely to develop cancer. CT […] CT radiation increases the risk by 24 per cent, and the risk rises by an additional 16 per cent each time the child has a scan, researchers found.

Although the researchers say the risk is small, their discovery does emphasize that CT imaging should be done more sparingly and only in cases where it is absolutely necessary. BMJ, 2013; 346: f2360

CT scans – X-ray computed tomographyW, technically – are scans that combine numerous X-ray images to form a three-dimensional picture of the soft tissues, slice by slice. They are an important diagnostic tool and can identify potentially life-threatening conditions such as subdural haematomaW. The primary use of CT scans is head CT, usually following head trauma. In adults this is quite low risk but in children the brain is still growing, so the risk is higher (and this has been known for a long time).

The term “CT radiation” is classic framing, of the type WDDTY routinely engage in. CT involves X-rays, X-rays are radiation, this is not a secret, but “CT radiation” invokes the radiation bogeyman for additional fearmongering effect.

The fact that X-rays involve ionising radiation and hence a risk of cancer, is well-known and forms part of the informed consent process for the procedure.

With X-rays generally and CT scans in particular there is a balance to be struck between risk and benefit. The BMJ article puts some figures on that.

It also uses relative risk. The BMJ paper is based on Australian data but finds similar results to the US and British data in the Lancet last year (see below).

It also makes this interesting point:

Our study shows that CT scans during childhood and adolescence are followed by an increase in cancer incidence for all cancers combined and for many individual types of cancer. We cannot, however, necessarily assume that all the excess cancers seen during the current period of follow-up were caused by CT scans, because scanning decisions are based on medical indications and are not allocated at random. Thus, we cannot rule out the possibility of reverse causation, whereby symptoms of precancerous conditions (including genetic conditions) or early symptoms of the cancer itself might themselves prompt a CT scan. Such reverse causation is most likely to be present for brain cancers following a brain CT, where low-grade cancers could lead to symptoms prompting investigation several years before the eventual diagnosis of cancer.

This is good data and worth knowing, but not really a novel finding. A paper in The Lancet in 2012 states:

During follow-up, 74 of 178,604 patients were diagnosed with leukaemia and 135 of 176,587 patients were diagnosed with brain tumours. We noted a positive association between radiation dose from CT scans and leukaemia […]

Because these cancers are relatively rare, the cumulative absolute risks are small: in the 10 years after the first scan for patients younger than 10 years, one excess case of leukaemia and one excess case of brain tumour per 10,000 head CT scans is estimated to occur.

So the scans increase a tiny risk to a slightly less tiny risk. Whereas acute subdural haematoma is always a medical emergency requiring prompt surgical intervention to avoid coma or permanent brain damage.

This research was funded by the US National cancer Institute and the UK Department of Health – so not only is the medical establishment not suppressing this information, they are primarily responsible for ensuring that it’s available.

It’s a matter of clinical judgement and informed consent.

What WDDTY don’t tell you is the alternatives. Dowsing, perhaps?

What Doctors Don't Tell You
Why don’t doctors tell you that CT scans involve radiation and a risk of cancer?

They do. It’s right there on the consent form.

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