title: A prospective study of medical diagnostic radiography and risk of thyroid cancer.
abstract: Although diagnostic x-ray procedures provide important medical benefits, cancer risks associated with their exposure are also possible, but not well characterized. The US Radiologic Technologists Study (1983-2006) is a nationwide, prospective cohort study with extensive questionnaire data on history of personal diagnostic imaging procedures collected prior to cancer diagnosis. We used Cox proportional hazard regressions to estimate thyroid cancer risks related to the number and type of selected procedures. We assessed potential modifying effects of age and calendar year of the first x-ray procedure in each category of procedures. 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 thyroid cancer risk associated with diagnostic x-rays except for dental x-rays. We observed a 13% increase in thyroid cancer risk for every 10 reported dental radiographs (hazard ratio = 1.13, 95% confidence interval: 1.01, 1.26), which was driven by dental x-rays first received before 1970, but we found no evidence that the relationship between dental x-rays and thyroid cancer was associated with childhood or adolescent exposures as would have been anticipated. The lack of association of thyroid cancer with x-ray procedures that expose the thyroid to higher radiation doses than do dental x-rays underscores the need to conduct a detailed radiation exposure assessment to enable quantitative evaluation of risk.
authors.affiliation: Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD, USA. netagil@mail.nih.gov
authors.forename: Gila
authors.initials: G
authors.lastname: Neta
authors.forename: Preetha
authors.initials: P
authors.lastname: Rajaraman
authors.forename: Amy
authors.initials: A
authors.lastname: Berrington de Gonzalez
authors.forename: Michele M
authors.initials: MM
authors.lastname: Doody
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Alexander
authors.forename: Dale
authors.initials: D
authors.lastname: Preston
authors.forename: Steven L
authors.initials: SL
authors.lastname: Simon
authors.forename: Dunstana
authors.initials: D
authors.lastname: Melo
authors.forename: Jeremy
authors.initials: J
authors.lastname: Miller
authors.forename: D Michal
authors.initials: DM
authors.lastname: Freedman
authors.forename: Martha S
authors.initials: MS
authors.lastname: Linet
authors.forename: Alice J
authors.initials: AJ
authors.lastname: Sigurdson
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications; D016017:Odds Ratio; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011859:Radiography / Q000009:adverse effects; D011861:Radiography, Dental / Q000009:adverse effects; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D011795:Surveys and Questionnaires; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D014481:United States / Q000453:epidemiology; D014965:X-Rays / Q000009:adverse effects*