X-rays linked to thyroid cancer

A collaborative study by scientists from Brighton, Cambridge and Kuwait found that the risk of the cancer rose with increasing numbers of dental X-rays.

Researchers said the notion that low-dose radiation exposure through dental radiography is absolutely safe now needs to be investigated further.

And they added that their study highlighted concern that dental X-rays should only be prescribed when the patient has a specific clinical need, and not as part of a routine check-up.

The thyroid gland - situated in the neck - is known to be sensitive to ionising radiation, particularly in children, and dental radiography is often overlooked as a potential hazard to the gland, the team said.

About 1,900 new cases of thyroid cancer are diagnosed each year in Britain and the incidence rates more than doubled between 1975 and 2006.

Researchers, led by Dr Anjum Memon, of the Brighton and Sussex Medical School, said the increasing use of sensitive diagnostic techniques is not believed to account for all of the rise and that other causes warrant investigation.

The team studied 313 thyroid cancer patients in Kuwait where the numbers of thyroid cancer are relatively high compared with Britain.

They said the results of their work, although the largest case-control study on the subject, should be treated with caution because the data was based on self-reporting by the participants and comprehensive historical dental X-ray records were not available from the clinics.

But Dr Memon said the findings were consistent with previous reports of increased risk of thyroid cancer in dentists, dental assistants and X-ray workers, suggesting multiple low-dose exposures in adults may be important.

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