title: Diagnostic X-rays and risk of childhood leukaemia.
abstract: BACKGROUND
  The association between diagnostic X-ray exposures early in life and increased risk of childhood leukaemia remains unclear.
  
  
  METHODS
  This case-control study included children aged 0-14 years diagnosed with acute lymphoid leukaemia (ALL, n = 711) or acute myeloid leukaemia (AML, n = 116) from 1995 to 2008. Controls were randomly selected from the California birth registry and individually matched to cases with respect to date of birth, sex, Hispanic ethnicity and maternal race. Conditional logistic regression analyses were performed to assess whether ALL or AML was associated with self-reported child's X-rays after birth (post-natal), including number of X-rays, region of the body X-rayed and age at first X-ray, as well as maternal X-rays before and during pregnancy (preconception and prenatal).
  
  
  RESULTS
  After excluding X-rays in the year prior to diagnosis (reference date for matched controls), risk of ALL was elevated in children exposed to three or more post-natal X-rays [odds ratio (OR) = 1.85, 95% confidence interval (CI) 1.12-2.79]. For B-cell ALL specifically, any exposure (one or more X-rays) conferred increased risk (OR = 1.40, 95% CI 1.06-1.86). Region of the body exposed was not an independent risk factor in multivariable analyses. No associations were observed between number of post-natal X-rays and AML (OR = 1.05, 95% CI 0.90-1.22) or T-cell ALL (OR = 0.84, 95% CI 0.59-1.19). Prevalence of exposure to prenatal and preconception X-rays was low, and no associations with ALL or AML were observed.
  
  
  CONCLUSIONS
  The results suggest that exposure to post-natal diagnostic X-rays is associated with increased risk of childhood ALL, specifically B-cell ALL, but not AML or T-cell ALL. Given the imprecise measures of self-reported X-ray exposure, the results of this analysis should be interpreted with caution and warrant further investigation.
authors.affiliation: School of Public Health, University of California, Berkeley, CA, USA. kbartley@berkeley.edu
authors.forename: Karen
authors.initials: K
authors.lastname: Bartley
authors.forename: Catherine
authors.initials: C
authors.lastname: Metayer
authors.forename: Steve
authors.initials: S
authors.lastname: Selvin
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ducore
authors.forename: Patricia
authors.initials: P
authors.lastname: Buffler
mesh_terms: D000293:Adolescent; D002140:California / Q000453:epidemiology; D016022:Case-Control Studies; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D007223:Infant; D007231:Infant, Newborn; D015470:Leukemia, Myeloid, Acute / Q000453:epidemiology / Q000209:etiology*; D016015:Logistic Models; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000453:epidemiology / Q000209:etiology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology / Q000209:etiology*; D011859:Radiography / Q000009:adverse effects*; D012042:Registries; D012307:Risk Factors