Report: Past dental X-rays increase risk of brain tumours

People who received frequent dental X-rays in the past have an increased risk of developing the most commonly diagnosed brain tumour in the United States, according to a recent study.

The findings of the study published in CANCER, a peer-reviewed journal of the American Cancer Society, suggest that moderate use of dental X-rays may be of benefit to some patients.

Ionising radiation is the primary environmental risk factor for developing meningioma, the most frequently diagnosed brain tumour in the US. Those types of brain tumours, which account for one-third of all brain tumours diagnosed in the US, are mostly non-cancerous.

Dr. Elizabeth Claus of the Yale University School of Medicine in New Haven, Connecticut and Brigham and Women’s Hospital in Boston and her colleagues studied 1,433 patients in the US who were diagnosed with meningioma brain tumours between the ages of 20 and 79 years between 2006 and 2011. They also studied information from a control group of 1,350 people with similar characteristics, but who had not been diagnosed with a brain tumour.

Over a lifetime, patients with the disease were more than twice as likely as those in the control group to report having ever had a bite-wing exam, which uses an X-ray film held in place by a tab between the teeth. Individuals who reported receiving bite-wing exams on a yearly or more frequent basis were 1.4 to 1.9 times as likely to develop meningioma as controls. Risks differed depending on the age at which the exams were done.

An increased risk of meningioma was also linked with panorex exams, which are taken outside of the mouth and show all of the teeth on one film, taken at a young age or on a yearly or more frequent basis. Individuals who reported receiving these exams when they were younger than 10 years old had a 4.9 times increased risk of developing meningioma. Those who reported receiving them on a yearly or more frequent basis were 2.7 to 3.0 times, depending on age, as likely to develop meningioma as controls.

The researchers noted that today’s dental patients are exposed to lower doses of radiation than in the past. Nonetheless, “the study presents an ideal opportunity in public health to increase awareness regarding the optimal use of dental X-rays, which, unlike many risk factors, is modifiable,” Dr. Claus said.

“Specifically, the American Dental Association’s guidelines for healthy persons suggest that children receive one X-ray every one to two years, teens receive one X-ray every one and a half to three years, and adults receive one X-ray every two to three years. Widespread dissemination of this information allows for increased dialogue between patients and their health care providers,” she added.

In response to the study, the American Dental Association issued a statement noting that the interviews relied on participants’ memories of how often they had different types of X-rays years earlier.

“Studies have shown that the ability to recall information is often imperfect. Therefore, the results of studies that use this design can be unreliable because they are affected by what scientists call “recall bias.” Also, the study acknowledges that some of the subjects received dental X-rays decades ago when radiation exposure was greater. Radiation rates were higher in the past due to the use of old X-ray technology and slower speed film. The ADA encourages further research in the interest of patient safety,” the statement read.

It continued: “The ADA’s long-standing position is that dentists should order dental X-rays for patients only when necessary for diagnosis and treatment. Since 1989, the ADA has published recommendations to help dentists ensure that radiation exposure is as low as reasonably achievable.”

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