cancer risk in children exposed to ct scans

CANCER RISK IN CHILDREN CANCER RISK IN CHILDREN EXPOSED TO CT SCANSEXPOSED TO CT SCANS

Allison Low3.10.2013

Clinical Question• Do CT scans in children and adolescents increase

their subsequent risk of developing cancer?• P - children and adolescents• I - CT scans• C - no CT scans• O - cancer

Clinical cases• 13 year old boy with an incidental finding of

papilloedema, neurological examination otherwise normal

• 4 year old girl, RTA, GCS of 9, visible head injury, no external abdominal injuries, haemodynamically stable

Current practice

Methods• population based, cohort, data linkage study• Australia• 10.9 million people aged 0-19 (Medicare) over a 20

year period ending in 2005• monitoring until 2007

Methods• Medicare records record all (funded) CT scans• Australian Cancer Database (ICD-10 codes)• socioeconomic status from SEIFA

Methods - missed scans• state-based tertiary hospitals (not on records)• scans outside of Australia

Analysis• one year lag period (also five and ten year lags)• IRRs exposed vs unexposed• dosage: estimate by site, year of scan, age (changed

after 2001)

Results

Scans in exposed patients

Results• mean length of follow up: 17.3 years (unexposed), 9.5

years (exposed)• 3150 exposed individuals developed cancer• 57 524 non-exposed developed cancer• overall, IRR 24% higher in exposed group (IRR 1.24,

95% CI 1.20-1.29)

Main results

Other results• IRR increased with each additional CT scan (0.16 ,

95% CI 0.13-0.19)• IRR increased for all cancers combined, also for all

solid organ cancers, all lymphoid and haematopoeitic cancers

• site-specific eg leukaemia after CT abdo/pelvis• gender difference for non-brain solid organ tumours:

F>M (1.23)• socioeconomic status: no significant difference

Brain cancer• brain cancer - highest risk 1-4 years after exposure,

higher risk for 15 years• under five years riskiest• ? reverse causation - analysis repeated excluding all

brain cancers after CT brain - 1.20, 95% CI 1.15-1.24

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Discussion points• (no trauma CT patients with subsequent leukaemia in

Sheffield...)• Image Gently/ALARA• CT scans vs clinical skill