Development of cancer risk estimation code due to radiation exposure, 3; Verification and perspective

Kai, Michiaki*; Shimada, Kazumasa ; Kudo, Shinichi*; Furukawa, Kyoji*; Satoh, Daiki   ; Takahara, Shogo  ; Takagi, Shunji*; Sasaki, Michiya*

This presentation is the third in a series of three presentations on the results of the "Expert Group on the Development of Cancer Risk Estimation Codes Associated with Radiation Exposure" established by the Japan Health Physics Society, which examines the parameters employed in the codes and the calculation results, and summarizes the future prospects of the codes. In order to calculate cumulative excess risk (CER) as a measure of lifetime risk with confidence intervals, a variance-covariance matrix for the parameters of the risk model is required. However, in a study conducted by the Radiation Effects Research Foundation using the regression analysis program Epicure on large-scale epidemiological data from A-bomb survivors, the variance-covariance matrix was not disclosed. Therefore, in this study, we independently derived parameters and covariance matrices using a generalized linear model (GLM) and confirmed that the parameter values agreed well with the Epicure results. The CERs calculated using the derived parameters and covariance matrices were compared with those calculated by the U.S. code RadRAT. Although a simple comparison is not possible due to the different population baselines of the two codes, they were found to be in general agreement. The developed code is expected to contribute to the discussion of influence factors and uncertainty in risk assessment.