Interactive RadioEpidemiological Program

Interactive RadioEpidemiological Program
IREP v.5.4

IREP 5.4 Upgrade (12/04/08)

1. Corrected Acute Lymphocytic Leukemia Algorithm
It was identified that IREP contained an incorrect algorithm for a specific set of input parameters used when calculating assigned share (probability of causation) for acute lymphocytic leukemia cases. For all types of leukemias (including acute lymphocytic leukemia), in the case of acute exposure to low-LET radiation, the dose response obtained from the epidemiological data is linear-quadratic. Therefore, the ERR should be a function of [dose*(1+dose)]. In versions of IREP prior to v.5.4, the ERR for acute lymphocytic leukemia was programmed to depend only on dose instead of using the linear-quadratic algorithm. This modification has the potential to slightly increase the assigned share results for acute lymphocytic leukemia cases, if the case included acute exposures to low-LET radiation.

2. Corrected Age Dependency for Selected Cancers
A small difference was identifed between the IREP code and its documentation. The difference occurred in an algorithm that models the uncertainty in the adjustment factor describing the dependency of risk on age at exposure and attained age for cancer types included in Group 2. The IREP code has been modified to match the documentation. The assigned share values estimated for Group 2 cancers using IREP v.5.4 are identical to the results obtained from previous versions of IREP for any cancers diagnosed at ages 50 or older, and for any radiation exposures that occurred at ages 30 or older. The modification has the potential of reducing the uncertainty in the estimated assigned share for exposures at ages less than 30 and for cancers diagnosed at ages less than 50.

3. Dose Rounding Algorithm on Summary Page
The dose input parameters that are summarized on the "Summary Report" page have now been rounded to 3 significant figures. Prior versions of IREP reported all digits of the dose parameters. If the dose value is less than 0.001 or larger than 1000 cSv, exponential format is now used in the dose summary table.

Previous IREP Upgrades

1. Random Errors in Dosimetry for Radon Exposures (01/21/05)
The radon model in previous versions of IREP contained a bias correction factor for random errors in dosimetry for smokers. It has been determined that the bias correction factor should also be applied for individuals who have never smoked. This modification, which affects only lung cancer cases for never smokers who were exposed to radon, has the potential to increase assigned share. The actual effect on the assigned share varies according to the level of exposure to radon.

2. Modification for thyroid cancer (03/19/04)
Previous versions of IREP contained a reduction of the risk coefficients for thyroid cancer for ages less than 20 to account for a perceived difference in the dose response from exposure to x-rays and the dose response from exposure to high-energy gamma rays. More recent interpretation of the epidemiologic data on thyroid cancer from exposure to x-rays indicates that such a reduction is not necessary and should be removed from IREP. This modification only affects individuals with thyroid cancer who were exposed at ages less than 20 and leads to an increase in the estimated assigned share.

3. Modification for bone cancer (05/11/03)
Previous versions of IREP assumed a latency period for bone cancer of approximately 10 years, similar to the latency period of other solid tumors. More recent interpretation of epidemiologic studies indicates that bone cancer can occur as early as 5 years after exposure to radiation, similar to thyroid cancer. Based on this finding, a reduction in the latency period assigned for bone cancer has been changed from that of solid tumors (about 10 years) to that of thyroid cancer (about 5 years). This modification only affects individuals who developed bone cancer within about 10 years after exposure to radiation and leads to an increase in assigned share.