Effect of Recent Changes in Atomic Bomb Survivor Dosimetry on Cancer Mortality Risk Estimates

Abstract

The Radiation Effects Research Foundation has recently implemented a new dosimetry system, DS02, to replace the previous system, DS86. This paper assesses the effect of the change on risk estimates for radiation-related solid cancer and leukemia mortality. The changes in dose estimates were smaller than many had anticipated, with the primary systematic change being an increase of about 10% in gamma-ray estimates for both cities. In particular, an anticipated large increase of the neutron component in Hiroshima for low-dose survivors did not materialize. However, DS02 improves on DS86 in many details, including the specifics of the radiation released by the bombs and the effects of shielding by structures and terrain. The data used here extend the last reported follow-up for solid cancers by 3 years, with a total of 10,085 deaths, and extends the follow-up for leukemia by 10 years, with a total of 296 deaths. For both solid cancer and leukemia, estimated age-time patterns and sex difference are virtually unchanged by the dosimetry revision. The estimates of solid-cancer radiation risk per sievert and the curvilinear dose response for leukemia are both decreased by about 8% by the dosimetry revision, due to the increase in the gamma-ray dose estimates. The apparent shape of the dose response is virtually unchanged by the dosimetry revision, but for solid cancers, the additional 3 years of follow-up has some effect. In particular, there is for the first time a statistically significant upward curvature for solid cancer on the restricted dose range 0-2 Sv. However, the low-dose slope of a linear-quadratic fit to that dose range should probably not be relied on for risk estimation, since that is substantially smaller than the linear slopes on ranges 0-1 Sv, 0-0.5 Sv, and 0- 0.25 Sv. Although it was anticipated that the new dosimetry system might reduce some apparent dose overestimates for Nagasaki factory workers, this did not materialize, and factory workers have significantly lower risk estimates. Whether or not one makes allowance for this, there is no statistically significant city difference in the estimated cancer risk.

Second cancer risk after radiation therapy of ependymoma using the flattening filter free irradiation mode of a linear accelerator

“…In the low‐dose region, the EAR presents a linear dose–response 19, 20. Since planning CT data do not include images at larger distances for reasons of radiation protection, no calculations of the EAR based on DVH are possible, for example, bladder, bowel, and gonads.…”

Height loss starting in middle age predicts increased mortality in the elderly

“…We used individual radiation dose estimates on the Radiation Effects Research Foundation's Dosimetry System 2002 (DS02). (31) For the mortality analysis, we used the PHREG procedure in SAS program (SAS version 9.1, SAS Institute Inc, Cary, NC, USA), with stratification by 5-year intervals of baseline age, for estimation of the parameters and testing. With consideration for parameter distributions, we tested differences between the alive group and the death group using Student's t-tests for continuous variables and x 2 tests for categorical variables.…”

Characteristic expression of fukutin in gastric cancer among atomic bomb survivors

“…Precise estimation of radiation dose in the LSS cohort required a complicated system with numerous criteria (20). The LSS cohort from the RERF is based on the DS02 system, which was established by the Joint US-Japan Working Group, a collaboration among American, German and Japanese universities together with national laboratories (20).…”

“…The HUH cohort of 86 patients with GC were also LSS cohort members, and therefore atomic bomb radiation doses were estimated using the DS02 system (20). These patients were classified into two groups according to the levels of exposed radiation dose: The high dose-exposed group (≥5 mGy) and the low dose-exposed group (<5 mGy).…”

“…However, there was no association between fukutin expression and exposure status. Therefore, analysis of fukutin expression levels in the HUH cohort was performed, as these patients were LSS cohort members, in which atomic bomb radiation doses were estimated correctly by the DS02 system (20). All 86 patients were atomic bomb survivors in Hiroshima and were comprised of 44 high dose-exposed and 42 low dose-exposed patients, who developed GC following the bombing.…”