Calculation methodology and perspectives on the evolution of radiation detriment have been reviewed recently by ICRP Task Group 102 on Detriment Calculation Methodology in ICRP Publication 152 (2022, in press). The Task Group performed an in-depth review of detriment calculation as presented in ICRP Publication 103, detailing each step of detriment calculation, associated parameters, models, and hypothesis.
Detriment calculation methodology is a two steps process as detailed in (Clero et al., J Radiol Prot 2019, 2022). The first step to calculate nominal cancer risk coefficients for a set of organs and tissues, plus heritable effects. The second step is a weighting for cancer severity, based on judgements concerning lethality, quality of life, and years of life lost, to estimate detriment values for each organ or tissue. After standardisation of organ-specific detriments to obtain relative detriments, the overall radiation detriment is calculated as the sum of relative detriments, i.e., the relative contribution of each organ or tissue to the total radiation detriment is used to derive tissue weighting factors used for the calculation of effective dose.
The Task Group 102 will also consider potential improvements to the calculation methodology with regard to the development of the future ICRP General Recommendations.
The current General Recommendations of ICRP were elaborated nearly 15 years ago. Detriment calculation methodology requires revision to reflect the evolution of scientific knowledge and guarantee adequate expert judgements in the ongoing process of revision of the system of Radiological Protection (Clement et al., J Radiol Prot 2021).
The main objective of the Task Group is to evaluate the current knowledge on all aspects involved in the calculation of detriment for cancer, to assess the implications of updating components of detriment calculation where necessary and to consider potential modifications of detriment calculation. The objectives are specified below.
Several Task Groups have been or will be launched to consider specific and complementary aspects of the detriment. Specifically, Task Group 91 is dealing with the Dose and Dose Rate Effectiveness Factor (DDREF), Task Group 118 with relative biological effectiveness, Task Group 119 with diseases of the circulatory system, and Task Group 121 with the effects of ionising radiation exposure in offspring and next generations. These elements of the detriment will not be considered in the present Task Group.
1. Cancer risk models
Risk estimates in ICRP Publication 103 principally relied on Life Span Stucy (LSS) incidence data gathered up to the end of 1998 (Clero et al., J Radiol Prot 2019, 2022). The LSS as well as other cohorts have been updated since then, and new studies have been conducted. The objectives in this section are:
2. Calculation of nominal risks
The second step of the calculation of radiation detriment deals with the methodology and parameters used to calculate the nominal risk coefficients. The objectives in this section are:
3. Weighting scheme for cancer severity
The objectives of the Task Group in this section are:
4. Reference population
The current detriment calculation process relies on risk models (mainly derived from a Japanese population), baseline rates (derived from 2 composite populations from Asia and Europe-North America), and lethality and severity parameters for cancer (derived from the USA). However, the interpretation of the current detriment is global. The objectives in this section are:
5. Suggestions for modifying the detriment calculation scheme for cancer
The results of the previous sections will be integrated into suggestions for a revised detriment calculation scheme for cancer. The objectives in this section are:
In a first step, a kick-off in person Task Group meeting is planned to discuss ideas, identify important issues to be addressed, and finalize the programme of work of the Task Group.
In a second step, the Task Group will prepare a detailed report. The report will include a review of the current knowledge of risk models, methods to calculate nominal risks, weighting risks according to their health consequences, and stratification of both with regard to populations. Finally, the report will provide recommendations for further action, for all Committees and the Main Commission.
The Task Group will liaise with the UNSCEAR to exploit potential synergism with the CanEpi expert group on “Epidemiological studies on radiation and cancer”.
The Task Group will develop an ICRP publication that addresses the objectives described above. The major sections of the report will cover updates of cancer risk models, approaches to weight the severity of cancers and the application of risk and severity measures on a global population.
An open on-line Webinar will be organised by ICRP at the time of publication to summarize the main elements of the report.
In addition, the Task Group will develop materials suitable for ICRPædia in collaboration with the Scientific Secretariat.
|Ludovic Vaillant (Co-Chair), CEPN, France|
|Richard Wakeford (Co-Chair), The University of Manchester, United Kingdom|