title: Are the studies on cancer risk from CT scans biased by indication? Elements of answer from a large-scale cohort study in France.
abstract: BACKGROUND
  Recent epidemiological results suggested an increase of cancer risk after receiving computed tomography (CT) scans in childhood or adolescence. Their interpretation is questioned due to the lack of information about the reasons for examination. Our objective was to estimate the cancer risk related to childhood CT scans, and examine how cancer-predisposing factors (PFs) affect assessment of the radiation-related risk.
  
  
  METHODS
  The cohort included 67,274 children who had a first scan before the age of 10 years from 2000 to 2010 in 23 French departments. Cumulative X-rays doses were estimated from radiology protocols. Cancer incidence was retrieved through the national registry of childhood cancers; PF from discharge diagnoses.
  
  
  RESULTS
  During a mean follow-up of 4 years, 27 cases of tumours of the central nervous system, 25 of leukaemia and 21 of lymphoma were diagnosed; 32% of them among children with PF. Specific patterns of CT exposures were observed according to PFs. Adjustment for PF reduced the excess risk estimates related to cumulative doses from CT scans. No significant excess risk was observed in relation to CT exposures.
  
  
  CONCLUSIONS
  This study suggests that the indication for examinations, whether suspected cancer or PF management, should be considered to avoid overestimation of the cancer risks associated with CT scans.
authors.affiliation: Laboratory of Epidemiology, Institute for Radiological Protection and Nuclear Safety, BP 17, 92262 Fontenay-aux-Roses, France.
authors.forename: N
authors.initials: N
authors.lastname: Journy
authors.affiliation: Medical Radiation Protection Expertise Unit, Institute for Radiological Protection and Nuclear Safety, BP 17, 92262 Fontenay-aux-Roses, France.
authors.forename: J-L
authors.initials: JL
authors.lastname: Rehel
authors.affiliation: Department of Paediatric Radiology, Trousseau University Hospital, 26 avenue du Docteur Arnold-Netter, 75012 Paris, France.
authors.forename: H
authors.initials: H
authors.lastname: Ducou Le Pointe
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institute of Health, 9000 Rockville Pike, 20892 Bethesda, MD, USA.
authors.forename: C
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Radiology, Institut Curie, 11-13 rue Pierre et Marie Curie, 75005 Paris, France.
authors.forename: H
authors.initials: H
authors.lastname: Brisse
authors.affiliation: Department of Paediatric Radiology, Pellegrin University Hospital, Place Amélie Raba-Léon, 33000 Bordeaux, France.
authors.forename: J-F
authors.initials: JF
authors.lastname: Chateil
authors.affiliation: Laboratory of Epidemiology, Institute for Radiological Protection and Nuclear Safety, BP 17, 92262 Fontenay-aux-Roses, France.
authors.forename: S
authors.initials: S
authors.lastname: Caer-Lorho
authors.affiliation: Laboratory of Epidemiology, Institute for Radiological Protection and Nuclear Safety, BP 17, 92262 Fontenay-aux-Roses, France.
authors.forename: D
authors.initials: D
authors.lastname: Laurier
authors.affiliation: Laboratory of Epidemiology, Institute for Radiological Protection and Nuclear Safety, BP 17, 92262 Fontenay-aux-Roses, France.
authors.forename: M-O
authors.initials: MO
authors.lastname: Bernier
mesh_terms: D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D009369:Neoplasms / Q000453:epidemiology*; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*