A prospective study of medical diagnostic x-rays and risk of thyroid cancer

Thursday, October 11, 2012 — Poster Session III
10:00 a.m. – Noon	Natcher Conference Center, Building 45	NCI	EPID-18

* FARE Award Winner

Authors

• G Neta
• P Rajaraman
• A Berrington de Gonzalez
• MM Doody
• BH Alexander
• D Preston
• SL Simon
• D Melo
• J Miller
• DM Freedman
• MS Linet
• AJ Sigurdson

Abstract

While diagnostic x-rays provide important medical benefits, cancer risks associated with their exposure are also possible, but not well characterized. The U.S. Radiological Technologists study is a nationwide, prospective cohort with extensive questionnaire data on history of personal diagnostic imaging procedures collected prior to cancer diagnosis. Cox proportional hazards were used to estimate thyroid cancer (TC) risks related to the number and type of selected procedures. Potential modifying effects of age and calendar year of the first x-ray in each category of procedures were assessed. Incident thyroid cancers (n=251) were diagnosed among 75,494 technologists (1.3 million person-years, mean follow-up=17 years). Overall, there was no clear evidence of TC risks associated with diagnostic x-rays, except for dental x-rays. The authors observed a 13% increase in TC risk for every 10 reported dental x-rays (95%CI: 1.01-1.26), driven by dental x-rays first received before 1970, but no evidence that the relationship between dental x-rays and TC was associated with childhood or adolescent exposures as would have been anticipated. The lack of association of TC with x-rays which expose the thyroid to higher radiation doses than dental x-rays underscores the need to conduct a detailed radiation exposure assessment to enable quantitative evaluation of risk.

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