Improved Estimates of Cancer Site-Specific Risks for A-Bomb Survivors

Abstract

Pawel, D. J., Preston, D. L., Pierce, D. A. and Cologne, J. B. Improved Estimates of Cancer Site-Specific Risks for A-Bomb Survivors. Radiat. Res. 169, 87-98 (2008). Simple methods are investigated for improving summary site-specific radiogenic risk estimates. Estimates in this report are derived from cancer incidence data from the Life Span Study (LSS) cohort of A-bomb survivors that are followed up by the Radiation Effects Research Foundation (RERF). Estimates from the LSS of excess relative risk (ERR) for solid cancer sites have typically been derived separately for each site. Even though the data for this are extensive, the statistical imprecision in site-specific (organ-specific) risk estimates is substantial, and it is clear that a large portion of the site-specific variation in estimates is due to this imprecision. Empirical Bayes (EB) estimates offer a reasonable approach for moderating this variation. The simple version of EB estimates that we applied to the LSS data are weighted averages of a pooled overall estimate of ERR and separately derived site-specific estimates, with weights determined by the data. Results indicate that the EB estimates are most useful for sites such as esophageal or bladder cancer, for which the separately derived ERR estimates are less precise than for other sites.

Fifth Warren K. Sinclair Keynote Address: Issues in Quantifying the Effects of Low-Level Radiation

“…For solid cancers the atomic bomb data now show dose responses that are predominantly linear over a dose range from one or two tenths of a gray to about 2 Gy (Preston et al 2007), while for leukemia there is clearer evidence of some upwards curvature over this dose range (Preston et al 2004). The data are also sufficient to provide reasonable quantification of solid cancer risks for individual tissues of the body (Pavel et al 2008). On this basis it has been possible for the International Commission on Radiological Protection (ICRP) to recommend meaningful dose limits and constraints, which have been implemented through strict regulations throughout the world, with consequent restriction and control of technical developments and practices in the uses of radiation; these regulations have undoubtedly prevented many malignancies from anthropogenic and natural sources of radiation.…”

Current Trends in Estimating Risk of Cancer from Exposure to Low Doses of Ionising Radiation

“…The LSS cohort of approximately 120,000 survivors (but for the most recent analysis, it was restricted to under 100,000) of the atomic bombings in Hiroshima and Nagasaki is the largest cohort selected for other reasons than disease or occupation. It includes both genders and all ages at exposure, whole-body exposure (mainly to external gamma rays, but a non-negligible ratio of neutrons was also present) with a wide range of doses (ranging from low doses relevant to diagnostic radiology to much higher, even lethal doses) and has a long follow-up period (more than 50 years), which makes it a very important and unique source of data for cancer risk assessment (5)(6)(7)(8). The first cancer associated with radiation in the LSS population was leukaemia and it has had the highest relative risk (ratio of the cancer rate in the irradiated group and cancer rate among the non-irradiated group) of any other cancer.…”

Cytogenetic Biological Dosimetry Past, Present and Future Perspectives

“…Moreover, the biological dosimetry, mortality rate, and the frequency of cancer and noncancer diseases were not measured in the same population, instead different population was employed as cohorts. Therefore, it is recommended to joint efforts between studies in biological dosimetry and epidemiology in order to elucidate on the role of induced chromosomal aberrations, cancer formation and cancer site-specific risks in cases of radiation over-exposure [39][40][41]. In addition, perspective area of further investigations in the field of biological consequences of Chernobyl accident for human health as well as Mayak and Techa River cohorts (low dose chronic exposure) seems to be further work on the radiation induced chromosome instability (transmissible, hidden, delayed) not only in irradiated persons but in their progeny [42] and so called "bystander effect", аs well as the evaluation of possible connection between the genome structure damages both stochastic (oncopathology) and non-stochastic (multifactorial pathology) radiation effects.…”