Problems of Identifying Dose – Effect Dependence for Radiation Carcinogenesis

Abstract

Purpose: Analysis of actual unresolved problems in the field of radiation epidemiology associated with establishing the dose–effect relationship (DER). Material and methods: The problem of establishing DER for ionizing radiation (IR) for the prognostic risk assessment based on the results of the performed biological and epidemiological studies is considered. The main characteristics of the cohorts, on which the epidemiological study (ES) was conducted, were analyzed. An algorithm is proposed for analyzing the statistical power of a real cohort in the plane with parameters accumulated dose – cohort strength, adjusted for the average duration of the cohort monitoring. Results: It is shown that among all the analyzed cohorts the following ones respond the criterion of lifetime detection of radiation solid cancers with the 95 % confidence: the victims of the atomic bombing of Japanese cities (LSS), personnel of the Mayak Plant, members of the Branch Medical Dosimetric Register (BMDR). Limitation of the observation period to 30 year dramatically reduces the statistical power of the ES observed effects. Overcoming of existing problems and improvement of quantitative presentation of the DER for IR can be achieved by a joint analysis of the results of already performed ES and (or) possible future ES. In this regard, it is very promising to carry out ES on the cohort of the Mayak personnel or BMDR as a whole. Conclusion: When planning new ESs and joint analyzes, the purpose of which is to improve our knowledge of DER in the required form and quality, one should proceed from the following provisions: – it is necessary to set the task for ES and, accordingly, for the construction of the DER model as a function of an age of exposure and an age of the oncological disease for a single exposure, taking into account the strict mathematical relationship between such dependencies of DER for single and extended impacts; – at the initial stage of the ES it is necessary, with the proposed algorithm, to verify the possibility of a statistical justification of the expected ES results. Averaged DER over the age of exposure is little suitable for predictive and comparative risk assessment.