Cancer Risk from CT Scans?

News — By on December 15, 2009 at 10:32 am

The risk of getting cancer from having a CT scan is under-estimated, and could be as high as 1 in 270 for young women undergoing certain types of heart scans, researchers say. A study carried out in California showed that the dose of radiation from a CT scan could be much higher than doctors expect. Risks were highest for women, especially women having scans of the chest, abdomen, and pelvis.
What do we know already?
Computed tomography scans (known as CT scans) use computers to build detailed pictures of the inside of your body, based on images taken using radiation. Because of the level of detail, they can be good at picking up small cancers, blood clots, or blockages in blood vessels that might otherwise go unseen.
In recent years, there’s been a trend towards using these types of scan more widely, especially in the US. For example, they might be used to investigate symptoms such as blood in the urine, which could be a sign of renal cancer but is much more likely to have a minor cause. Some private companies have advertised CT scans for healthy people, to pick up anything that might cause a problem in future.

But every CT scan involves a dose of radiation, and radiation can cause cancer. For most people, it’s unlikely that one scan would cause a cancer. But as CT scanning becomes more widespread, more people will be put at increased risk. Doctors wanted to know how much a CT scan would increase the risk of cancer for people having different types of scan, and at different ages.
The risk of getting cancer from a scan is higher in younger people, because they have their whole lives ahead in which a cancer may develop. For older people, who have less of their lives left to live, the risk is lower, because any changes to cells caused by radiation may not have time to develop into cancer during their lifetime.

Also, women are at increased risk of cancer from chest and abdomen scans, because of the risk of breast and gynaecological cancers.
Two new studies have just been published. One looked at the average amount of radiation people absorbed while having CT scans at 4 hospitals or clinics in California. They used this to calculate how much the scan would increase people’s lifetime risk of getting a cancer. The second study looked at how many scans were done across the US in 2007, and calculated how many future cancers might have been caused by those scans.
What do the new studies say?

The California study found that the amount of radiation people absorbed from different types of scan, at the different centres, varied quite a lot. In many cases, the average dose of radiation absorbed from a particular investigation was much higher than the figure usually quoted.

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