Multiple Dental X-rays Link To Increased Risk of Thyroid Cancer

By WebMD Health News
Researchers say initial findings suggest dental x-rays may have to be avoided as part of routine dental examinations

The risk of developing thyroid cancer increases with the number of dental x-rays that are taken, according to new research.

About 1,900 new cases of thyroid cancer are diagnosed each year in the UK and the incidence rates have more than doubled from 1.4 to 2.9 per 100,000 people between 1975 and 2006.

Radiation: ‘Overlooked’

The thyroid gland, which is in the neck, is exposed to radiation as a result of dental x-rays. It is known to be highly sensitive to ionising radiation, particularly in young children. The researchers from Brighton and Sussex Medical School say such diagnostic radiation is often overlooked as a potential hazard to the thyroid gland.

The researchers, led by Dr Anjum Memon, the School’s senior lecturer and consultant in public health medicine, studied 313 thyroid cancer patients in Kuwait, where dental treatment is free and where the incidence of thyroid cancer is relatively high compared to the UK.

Memon said the findings were consistent with previous reports of increased risk of thyroid cancer in dentists, dental assistants, and x-ray workers, which suggest that multiple low-dose exposures in adults may also be important. “The public health and clinical implications of these findings are particularly relevant in the light of increases in the incidence of thyroid cancer in many countries over the past 30 years,” he says.

Caution

However, the authors say the results of their study should be treated with caution because historical dental x-ray records were unavailable and the data were based on self-reporting by participants.

Memon calls for further investigation, using proper records that include the age of patients, frequency of exposure and dose given. “If the results are confirmed then the use of x-rays as a necessary part of evaluation for new patients, and routine periodic dental radiography (at 6-12 months interval), particularly for children and adolescents, will need to be reconsidered, as will a greater use of lead collar protection.”

Routine dental x-rays

The researchers say, if their initial results are confirmed, dental x-rays may have to be ruled out for routine oral health checks or when registering at a dental practice.

In an emailed statement, Henry Scowcroft, science information manager at Cancer Research UK, says: “The researchers themselves acknowledge that this study by no means proves a link between dental x-rays and thyroid cancer. To find out more about the causes of this rare cancer, larger more sophisticated studies would be needed.”

The latest research was funded by the Kuwait Foundation for the Advancement of Sciences (KFAS) and was administered by the Kuwait University Research Grant Administration. The findings appear in the journal Acta Oncologica.