Thyroid Cancer Following Childhood Low-Dose Radiation Exposure: A Pooled Analysis of Nine Cohorts.
The increased use of diagnostic and therapeutic procedures that involve radiation raises concerns about radiation effects, particularly in children and the radiosensitive thyroid gland.



Evaluation of relative risk (RR) trends for thyroid radiation doses <0.2 gray (Gy); evidence of a threshold dose; and possible modifiers of the dose-response, e.g., sex, age at exposure, time since exposure.



Pooled data from nine cohort studies of childhood external radiation exposure and thyroid cancer with individualized dose estimates, ≥1000 irradiated subjects or ≥10 thyroid cancer cases, with data limited to individuals receiving doses <0.2 Gy.



Cohorts included the following: childhood cancer survivors (n = 2); children treated for benign diseases (n = 6); and children who survived the atomic bombings in Japan (n = 1). There were 252 cases and 2,588,559 person-years in irradiated individuals and 142 cases and 1,865,957 person-years in nonirradiated individuals.



There were no interventions.



Incident thyroid cancers.



For both <0.2 and <0.1 Gy, RRs increased with thyroid dose (P < 0.01), without significant departure from linearity (P = 0.77 and P = 0.66, respectively). Estimates of threshold dose ranged from 0.0 to 0.03 Gy, with an upper 95% confidence bound of 0.04 Gy. The increasing dose-response trend persisted >45 years after exposure, was greater at younger age at exposure and younger attained age, and was similar by sex and number of treatments.



Our analyses reaffirmed linearity of the dose response as the most plausible relationship for "as low as reasonably achievable" assessments for pediatric low-dose radiation-associated thyroid cancer risk.
Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892.
Jay H
JH
Lubin
University of Rochester School of Medicine and Dentistry, Department of Public Health Sciences, Rochester, New York 14642.
M Jacob
MJ
Adams
Radiation Effects Research Foundation, Hiroshima 732-0815, Japan.
Roy
R
Shore
Department of Oncology and Radiation Physics and the Oncological Centre, Sahlgrenska University Hospital, S-413-45 Goteborg, Sweden.
Erik
E
Holmberg
University of Illinois College of Medicine, Section of Endocrinology, Diabetes, and Metabolism, Chicago, Illinois 60612.
Arthur B
AB
Schneider
Centre for Childhood Cancer Survivor Studies, Department of Public Health and Epidemiology, University of Birmingham, Birmingham B15 2TT, United Kingdom.
Michael M
MM
Hawkins
Department of Epidemiology and Cancer Control, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-3678.
Leslie L
LL
Robison
Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892.
Peter D
PD
Inskip
Department of Medical Physics, Radiumhemmet, Karolinska University Hospital and Karolinska Institute, SE-171 76 Stockholm, Sweden.
Marie
M
Lundell
Oncology, Department of Radiation Sciences, Umeå University, 901 87 Umeå, Sweden.
Robert
R
Johansson
Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892.
Ruth A
RA
Kleinerman
Cancer Epidemiology Research Unit, National Institute for Health and Medical Research-Institut Gustave Roussy, 94 805 Villejuif, France.
Florent
F
de Vathaire
Oncology, Department of Radiation Sciences, Umeå University, 901 87 Umeå, Sweden.
Lena
L
Damber
Cancer and Radiation Epidemiology Unit, Gertner Institute, Chaim Sheba Medical Center and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Tel Hashomer, 52621 Israel.
Siegal
S
Sadetzki
Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892.
Margaret
M
Tucker
Radiation Effects Research Foundation, Hiroshima 732-0815, Japan.
Ritsu
R
Sakata
Institute for Radiation Protection and Dosimetry, Brazilian Nuclear Energy Commission, 22783-127 Rio de Janeiro, Brazil.
Lene H S
LHS
Veiga
D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D009381:Neoplasms, Radiation-Induced / Q000175:diagnosis* / Q000453:epidemiology*; D011379:Prognosis; D000069079:Radiation Exposure / Q000009:adverse effects*; D018570:Risk Assessment; D012737:Sex Factors; D015996:Survival Rate; D013964:Thyroid Neoplasms / Q000453:epidemiology* / Q000209:etiology*