title: Risk of thyroid cancer after exposure to 131I in childhood.
abstract: BACKGROUND
  After the Chernobyl nuclear power plant accident in April 1986, a large increase in the incidence of childhood thyroid cancer was reported in contaminated areas. Most of the radiation exposure to the thyroid was from iodine isotopes, especially 131I. We carried out a population-based case-control study of thyroid cancer in Belarus and the Russian Federation to evaluate the risk of thyroid cancer after exposure to radioactive iodine in childhood and to investigate environmental and host factors that may modify this risk.
  
  
  METHODS
  We studied 276 case patients with thyroid cancer through 1998 and 1300 matched control subjects, all aged younger than 15 years at the time of the accident. Individual doses were estimated for each subject based on their whereabouts and dietary habits at the time of the accident and in following days, weeks, and years; their likely stable iodine status at the time of the accident was also evaluated. Data were analyzed by conditional logistic regression using several different models. All statistical tests were two-sided.
  
  
  RESULTS
  A strong dose-response relationship was observed between radiation dose to the thyroid received in childhood and thyroid cancer risk (P<.001). For a dose of 1 Gy, the estimated odds ratio of thyroid cancer varied from 5.5 (95% confidence interval [CI] = 3.1 to 9.5) to 8.4 (95% CI = 4.1 to 17.3), depending on the risk model. A linear dose-response relationship was observed up to 1.5-2 Gy. The risk of radiation-related thyroid cancer was three times higher in iodine-deficient areas (relative risk [RR]= 3.2, 95% CI = 1.9 to 5.5) than elsewhere. Administration of potassium iodide as a dietary supplement reduced this risk of radiation-related thyroid cancer by a factor of 3 (RR = 0.34, 95% CI = 0.1 to 0.9, for consumption of potassium iodide versus no consumption).
  
  
  CONCLUSIONS
  Exposure to (131)I in childhood is associated with an increased risk of thyroid cancer. Both iodine deficiency and iodine supplementation appear to modify this risk. These results have important public health implications: stable iodine supplementation in iodine-deficient populations may substantially reduce the risk of thyroid cancer related to radioactive iodines in case of exposure to radioactive iodines in childhood that may occur after radiation accidents or during medical diagnostic and therapeutic procedures.
authors.affiliation: International Agency for Research on Cancer, Lyon, France. cardis@iarc.fr
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Cardis
authors.forename: Ausrele
authors.initials: A
authors.lastname: Kesminiene
authors.forename: Victor
authors.initials: V
authors.lastname: Ivanov
authors.forename: Irina
authors.initials: I
authors.lastname: Malakhova
authors.forename: Yoshisada
authors.initials: Y
authors.lastname: Shibata
authors.forename: Valeryi
authors.initials: V
authors.lastname: Khrouch
authors.forename: Vladimir
authors.initials: V
authors.lastname: Drozdovitch
authors.forename: Evaldas
authors.initials: E
authors.lastname: Maceika
authors.forename: Irina
authors.initials: I
authors.lastname: Zvonova
authors.forename: Oleg
authors.initials: O
authors.lastname: Vlassov
authors.forename: André
authors.initials: A
authors.lastname: Bouville
authors.forename: Guennadi
authors.initials: G
authors.lastname: Goulko
authors.forename: Masaharu
authors.initials: M
authors.lastname: Hoshi
authors.forename: Alexander
authors.initials: A
authors.lastname: Abrosimov
authors.forename: Jadvyga
authors.initials: J
authors.lastname: Anoshko
authors.forename: Larisa
authors.initials: L
authors.lastname: Astakhova
authors.forename: Sergey
authors.initials: S
authors.lastname: Chekin
authors.forename: Evgenyi
authors.initials: E
authors.lastname: Demidchik
authors.forename: Rosaria
authors.initials: R
authors.lastname: Galanti
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ito
authors.forename: Elena
authors.initials: E
authors.lastname: Korobova
authors.forename: Evgenyi
authors.initials: E
authors.lastname: Lushnikov
authors.forename: Marat
authors.initials: M
authors.lastname: Maksioutov
authors.forename: Vladimir
authors.initials: V
authors.lastname: Masyakin
authors.forename: Alexander
authors.initials: A
authors.lastname: Nerovnia
authors.forename: Vladimir
authors.initials: V
authors.lastname: Parshin
authors.forename: Evgenyi
authors.initials: E
authors.lastname: Parshkov
authors.forename: Nikolay
authors.initials: N
authors.lastname: Piliptsevich
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Semyon
authors.initials: S
authors.lastname: Polyakov
authors.forename: Nina
authors.initials: N
authors.lastname: Shabeka
authors.forename: Eero
authors.initials: E
authors.lastname: Suonio
authors.forename: Vanessa
authors.initials: V
authors.lastname: Tenet
authors.forename: Anatoli
authors.initials: A
authors.lastname: Tsyb
authors.forename: Shunichi
authors.initials: S
authors.lastname: Yamashita
authors.forename: Dillwyn
authors.initials: D
authors.lastname: Williams
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D047852:Chernobyl Nuclear Accident; D002648:Child; D002675:Child, Preschool; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D015994:Incidence; D007455:Iodine / Q000172:deficiency*; D007457:Iodine Radioisotopes / Q000009:adverse effects*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D016017:Odds Ratio; D011193:Potassium Iodide / Q000008:administration & dosage; D002094:Republic of Belarus / Q000453:epidemiology; D018570:Risk Assessment; D012426:Russia / Q000453:epidemiology; D013961:Thyroid Gland / Q000528:radiation effects*; D013964:Thyroid Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control
chemical_list: D007457:Iodine Radioisotopes; D011193:Potassium Iodide; D007455:Iodine