title: Radiation treatment of patients with primary pediatric malignancies: risk of developing thyroid cancer as a secondary malignancy.
abstract: BACKGROUND
  The aim of this study was to estimate the risk of thyroid cancer as a secondary malignancy after radiation treatment of primary pediatric malignancies.
  
  
  METHODS
  Using the Surveillance, Epidemiology, and End Results database, we identified 7,670 patients from 1973 to 1988 with primary pediatric malignancies. The relative risk of thyroid cancer in irradiated patients was calculated using the Poisson regression model, and the Cox proportional hazards regression model was used for survival rates.
  
  
  RESULTS
  The relative risk (RR) of thyroid cancer for children who received radiation was 2.22 (95% confidence interval [CI], 1.15-4.29). It was highest for central nervous system cancer (RR = 4.47) and lowest for those with leukemia (RR = 1.75). Mortality was significantly reduced for patients who received radiation as children; the hazard ratio was .80 (95% CI, .75-.86).
  
  
  CONCLUSIONS
  Radiation for pediatric malignancies increases the risk of developing thyroid cancer as a secondary malignancy; however, these patients had localized disease and lower 20-year mortality.
authors.affiliation: Department of Surgery, University of Arizona School of Medicine, 1501 N Campbell Avenue, Office 4327, Tucson, AZ 85724, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Rose
authors.forename: Betsy C
authors.initials: BC
authors.lastname: Wertheim
authors.forename: Marlon A
authors.initials: MA
authors.lastname: Guerrero
mesh_terms: D000293:Adolescent; D016543:Central Nervous System Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007938:Leukemia / Q000401:mortality / Q000532:radiotherapy*; D008223:Lymphoma / Q000401:mortality / Q000532:radiotherapy*; D008297:Male; D009381:Neoplasms, Radiation-Induced / Q000209:etiology* / Q000401:mortality; D016609:Neoplasms, Second Primary / Q000209:etiology* / Q000401:mortality; D016017:Odds Ratio; D016012:Poisson Distribution; D016016:Proportional Hazards Models; D011878:Radiotherapy / Q000009:adverse effects; D012306:Risk; D018426:SEER Program; D013964:Thyroid Neoplasms / Q000209:etiology* / Q000401:mortality; D016896:Treatment Outcome