A Monte Carlo t Test to Evaluate Mesothelioma and Radiation in the US Transuranium and Uranium Registries

Our plain-English summary of A Monte Carlo t Test to Evaluate Mesothelioma and Radiation in the US Transuranium and Uranium Registries, by J.Y. Zhou, S.L. McComish, S.Y. Tolmachev (Health Physics, 2019).

The study

• Authors: J.Y. Zhou, S.L. McComish, S.Y. Tolmachev
• Journal: Health Physics
• Published: 2019;117(2):187-192
• Read it: PubMed · Publisher

Abstract

A cluster of nine mesothelioma cases was observed among 341 registrants' deaths in the US Transuranium and Uranium Registries. Descriptive analysis showed that mesothelioma cases had the highest average cumulative external radiation dose compared with lung cancer, other cancer, and noncancer deaths. Further analysis indicated that the mesothelioma cluster was very different demographically from lung cancer, other cancer, and noncancer deaths. Therefore, an internally matched case-control approach was applied to evaluate the differences in an average cumulative external radiation dose between mesothelioma deaths and other causes of death. A Monte Carlo t test was used to examine the statistical significance of the differences. The results showed that there were no significant statistical differences in an average cumulative external radiation dose between mesothelioma and lung cancer, other cancers, or noncancers for the internally matched cases and controls.

In plain English

This study looked at deaths among registrants of the US Transuranium and Uranium Registries, where nine mesothelioma deaths had occurred among 341 deceased registrants. Using the 287 deaths with dose records, the authors compared cumulative external radiation dose between mesothelioma deaths and deaths from lung cancer, other cancers, and noncancer causes. Before matching, the nine mesothelioma cases had the highest average dose, 174 mSv. They also had longer average employment, at 31 years. The authors then matched each mesothelioma case with white male controls of similar birth year, first hire year, age at death and years of employment. They tested the dose differences with a repeated-sampling (Monte Carlo) t test. Before matching, the results met the authors' criterion for a statistically significant difference. After matching they did not: 0%, 0% and 2.5% of the repeated tests were significant. After matching, the other-cancer controls had the highest average dose. The authors concluded there were no statistically significant differences in average dose for the matched cases and controls. They stated that the small, nonrandom registry data should not be generalized to US nuclear workers.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Internally matched case-control comparison within a registry of deceased workers, analyzed with a modified Monte Carlo (repeated random sampling) t test
• Who was studied: 287 of 341 deceased US Transuranium and Uranium Registries registrants who had cumulative external radiation dose records: 9 mesothelioma deaths, 31 lung cancer deaths, 62 other cancer deaths and 185 noncancer deaths. After matching, the mesothelioma cases were compared with 21 lung cancer, 31 other cancer and 37 noncancer matched controls. The analysis was done in 2015.
• Exposure: Cumulative external radiation dose (CERD, in mSv), taken from external radiation measurements in work records. Asbestos exposure was not analyzed in this study.
• Main results:
  • Before matching, the mesothelioma group had the highest average cumulative external radiation dose: 174 mSv (range 19 to 426 mSv). The lung cancer group averaged 105 mSv (t-test p = 0.066), the other cancer group 110 mSv (p = 0.054) and the noncancer group 153 mSv (p = 0.185).
  • The mesothelioma group had longer average employment, 31 years (range 19 to 43), compared with 24 years for lung cancer deaths, 22 years for other cancer deaths and 24 years for noncancer deaths.
  • Before matching, 17.5% (mesothelioma vs lung cancer), 20.0% (vs other cancers) and 5.4% (vs noncancer) of repeated t tests were statistically significant. Under the authors' criterion that 5% or more significant tests means a significant difference, all three comparisons counted as significant.
  • After matching, average doses were 155 mSv for the lung cancer controls, 181 mSv for the other cancer controls and 144 mSv for the noncancer controls. The other cancer controls then had a higher average than the mesothelioma group's 174 mSv.
  • After matching, 0% (vs lung cancer), 0% (vs other cancers) and 2.5% (vs noncancer) of repeated paired t tests were statistically significant. The authors reported these as statistically nonsignificant differences.
• The authors' conclusion: The authors concluded that, for the internally matched cases and controls, there were no statistically significant differences in average cumulative external radiation dose between mesothelioma and lung cancer, other cancers, or noncancers. They also concluded that the modified Monte Carlo t test offers a way to compare two groups of very unequal size.
• Limitations the authors state:
  • The small number of deaths, especially the 31 lung cancer deaths, limited matching, so relatively wide matching ranges had to be used.
  • Registry members are not representative of all US nuclear workers, and the registry was not designed for epidemiological analysis. The authors stated the results should not be generalized to US nuclear workers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Lung Cancer, Mesothelioma Cluster, Statistical Significance.

Related studies

• Analyses of radiation and mesothelioma in the US Transuranium and Uranium Registries — H. Gibb, K. Fulcher, et al. (2013)
• USTUR Special Session Roundtable-US Transuranium and Uranium Registries (USTUR): A Five-decade Follow-up of Plutonium and Uranium Workers — S.Y. Tolmachev, M.J. Swint, et al. (2019)
• Impact of chemical exposure on cancer mortality in a French cohort of uranium processing workers — S. Zhivin, D. Laurier, et al. (2013)
• Errors and blunders in the estimation of radiation exposure for the uranium miners of WISMUT in Germany — G.G. Eigenwillig (2006)
• Gibb et al. respond — H. Gibb, K. Fulcher, et al. (2014)
• Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS) — D.B. Richardson, E. Cardis, et al. (2015)

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