Journal of the National Cancer Institute Advance Access originally published online on March 11, 2008
JNCI Journal of the National Cancer Institute 2008 100(6):428-436; doi:10.1093/jnci/djn045
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© The Author 2008. Published by Oxford University Press.
ARTICLES |
Solid Cancer Incidence in Atomic Bomb Survivors Exposed In Utero or as Young Children
Affiliations of authors: Hirosoft International Corporation, Eureka, CA (DLP); Departments of Statistics (HC, SF) and Epidemiology (NN, FK), Radiation Effects Research Foundation (KK, RES), Hiroshima, Japan; Department of Epidemiology, Radiation Effects Research Foundation, Nagasaki, Japan (AS, MS); Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD (KM)
Correspondence to: Dale L. Preston, PhD, Hirosoft International Corporation, 1335 H St, Eureka, CA 95501-2331 (e-mail: preston{at}hirosoft.net).
Background: In utero exposure to radiation is known to increase risks of childhood cancers, and childhood exposure is associated with increased risks of adult-onset cancers. However, little is known about whether in utero exposure to radiation increases risks of adult-onset cancers.
Methods: Solid cancer incidence rates were examined among survivors of the atomic bombings of Hiroshima and Nagasaki who were in utero (n = 2452) or younger than 6 years (n = 15388) at the time of the bombings. Poisson regression was used to estimate and compare the levels and temporal patterns of the radiation-associated excess risks of first primary solid cancers among these survivors at ages 12–55. All statistical tests were two-sided.
Results: There were 94 eligible cancers in the in utero group and 649 in the early childhood group. The excess relative risk (ERR) increased with dose for both in utero (age 50, ERR = 1.0 per Sv, 95% confidence interval [CI] = 0.2 to 2.3 per Sv) and early childhood (age 50, ERR = 1.7 per Sv, 95% CI = 1.1 to 2.5 Sv) exposures. The ERR declined (P = .046) with increasing attained age in the combined cohort. Excess absolute rates (EARs) increased markedly with attained age among those exposed in early childhood but exhibited little change in the in utero group. At age 50, the estimated EARs per 10000 person-years per Sv were 6.8 (95% CI = <0 to 49) for those exposed in utero and 56 (95% CI = 36 to 79) for those exposed as young children.
Conclusions: Both the in utero and early childhood groups exhibited statistically significant dose-related increases in incidence rates of solid cancers. The apparent difference in EARs between the two groups suggests that lifetime risks following in utero exposure may be considerably lower than for early childhood exposure, but further follow-up is needed.
| CONTEXT AND CAVEATS Prior knowledge Exposure to ionizing radiation in utero and in childhood is associated with increased risks of cancers in childhood and in adulthood, respectively. Study design Excess risks of solid cancers at ages 12–55 among survivors of the atomic bombings of Hiroshima and Nagasaki who were in utero and young children at the time of the bombings were determined. Contributions Excess relative risks of solid cancers increased with radiation dose for both groups of survivors; they declined with increasing attained age in the combined cohort. Excess absolute rates increased with attained age among those who were exposed in childhood but remained steady among those exposed in utero. Implications The difference in excess absolute rates between the two groups of survivors suggests that lifetime risks after exposure may be lower for those exposed in utero than those exposed in childhood, but additional follow-up is necessary. Limitations Due to the limited population size available for analysis, data regarding temporal patterns and risks of site-specific cancers were not available.
|
Manuscript received September 13, 2007; revised December 12, 2007; accepted February 4, 2008.
Related Article in JNCI
CiteULike 
Connotea 
Del.icio.us What's this?
J Natl Cancer Inst 2008 100: 375.