Interactive Radioepidemiological Program (Irep): A Web-Based Tool for Estimating Probability of Causation/Assigned Share of Radiogenic Cancers

Abstract

The Interactive RadioEpidemiological Program (IREP) is a Web-based, interactive computer code that is used to estimate the probability that a given cancer in an individual was induced by given exposures to ionizing radiation. IREP was developed by a Working Group of the National Cancer Institute and Centers for Disease Control and Prevention, and was adopted and modified by the National Institute for Occupational Safety and Health (NIOSH) for use in adjudicating claims for compensation for cancer under the Energy Employees Occupational Illness Compensation Program Act of 2000. In this paper, the quantity calculated in IREP is referred to as “probability of causation/assigned share” (PC/AS). PC/AS for a given cancer in an individual is calculated on the basis of an estimate of the excess relative risk (ERR) associated with given radiation exposures and the relationship PC/AS = ERR/ERR+1. IREP accounts for uncertainties in calculating probability distributions of ERR and PC/AS. An accounting of uncertainty is necessary when decisions about granting claims for compensation for cancer are made on the basis of an estimate of the upper 99% credibility limit of PC/AS to give claimants the “benefit of the doubt.” This paper discusses models and methods incorporated in IREP to estimate ERR and PC/AS. Approaches to accounting for uncertainty are emphasized, and limitations of IREP are discussed. Although IREP is intended to provide unbiased estimates of ERR and PC/AS and their uncertainties to represent the current state of knowledge, there are situations described in this paper in which NIOSH, as a matter of policy, makes assumptions that give a higher estimate of the upper 99% credibility limit of PC/AS than other plausible alternatives and, thus, are more favorable to claimants.

Breast cancer risk in atomic bomb survivors from multi-model inference with incidence data 1958–1998

“…Compensation claims for cancer, i.e., from occupational exposure, are often based on the probability of causation. In the United States, the 99% confidence interval of this probability, which can be calculated with the IREP tool (Kocher et al 2008), is applied in court cases. In both areas, the credibility of risk assessment is improved by MMI, which combines predictions of several plausible models rather than relying on a single model of choice.…”

Therapy-related myelodysplastic syndromes, or are they?

“…It is very important to obtain a detailed exposure history to allow for qualitative risk assessment [8]. Detailed history of prior radiation is also equally important especially since quantitative risk-estimators for developing myeloid neoplasms after radiation exposure are available [9][10][11]. Integrating this information with known risk factors such as age at diagnosis and smoking history will potentially allow for a more accurate label of t-MN to be applied.…”

Implications of Claimant-Favorable Approaches Used in Dose and Probability of Causation Calculations Under Eeoicpa

“…As discussed elsewhere in this issue (Kocher et al 2008), IREP calculates the PC using a Monte Carlo approach for evaluating the uncertainty distributions associated with both cancer risk and dose estimates. In addition to the modeled uncertainty distributions, IREP contains inherently claimant-favorable assumptions and default parameters in certain instances.…”

“…The adoption of this approach to account for uncertainty in the dose and PC calculations seems to reflect Congress's discomfort with the government's previous practice of routinely opposing occupational illness claims based on radiological or toxic exposures. § As described in detail elsewhere in this issue (Kocher et al 2008), PC calculations are performed under Part B using the National Institute for Occupational Safety and Health (NIOSH) Interactive RadioEpidemiological Program (IREP) computer code. ** As shown by Toohey (2008), the differences between the 50 th and 99 th percentile PCs calculated by IREP can be significant, and are attributable to uncertainties in both the dose estimates and the risk of cancer induction associated with the assigned radiation types, energies, and exposure rates.…”