Bounding poorly characterized risks: a lung cancer example

Our plain-English summary of Bounding poorly characterized risks: a lung cancer example, by M. Ha-Duong, E.A. Casman, M.G. Morgan (Risk Analysis, 2004).

The study

• Authors: M. Ha-Duong, E.A. Casman, M.G. Morgan
• Journal: Risk Analysis
• Published: 2004;24(5):1071-83
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

For diseases with more than one risk factor, the sum of probabilistic estimates of the number of cases caused by each individual factor may exceed the total number of cases observed, especially when uncertainties about exposure and dose response for some risk factors are high. In this study, we outline a method of bounding the fraction of lung cancer fatalities not due to specific well-studied causes. Such information serves as a "reality check" for estimates of the impacts of the minor risk factors, and, as such, complements the traditional risk analysis. With lung cancer as our example, we allocate portions of the observed lung cancer mortality to known causes (such as smoking, residential radon, and asbestos fibers) and describe the uncertainty surrounding those estimates. The interactions among the risk factors are also quantified, to the extent possible. We then infer an upper bound on the residual mortality due to "other" causes, using a consistency constraint on the total number of deaths, the maximum uncertainty principle, and the mathematics originally developed of imprecise probabilities.

In plain English

This article was a methods demonstration, not a new study of patients or workers. The authors set out a mathematical way to cap the share of U.S. lung cancer deaths caused by poorly studied factors. From published literature, they gave ranges to three better-studied causes: smoking (active, former and passive) 70% to 95%, residential radon 2% to 21%, and occupational exposure to inhaled asbestos 1% to 5%. For asbestos, the authors' own estimate, based on mesothelioma deaths and the ratio of lung cancer to mesothelioma claims in asbestos lawsuits, was fewer than 5,560 occupational asbestos-related lung cancers in 2000, under 4% of 155,600 lung cancer deaths. Spontaneous (background) deaths were set at 3 per 100,000 and counted separately. The method then attributed 0% to 3.2% of lung cancer deaths to the group of other occupational and environmental pollutants. The authors concluded that, if the ranges for the well-understood causes are trusted, these other known and suspected lung carcinogens together account for no more than 3.2%. They noted that asbestos-related lung cancer statistics are not collected. They planned to gather expert opinion in future work.

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: Methods demonstration (mathematical bounding analysis) using values taken from published literature; no new data were collected
• Who was studied: Annual lung cancer deaths in the U.S. population as a whole (155,600 lung cancer deaths in 2000), not subgroups with different exposures
• Exposure: Four groups of causes: active, former and passive smoking; domestic (residential) radon; occupational exposure to inhaled asbestos (not broken down by fiber type in the analysis); and all other environmental and occupational risk factors combined
• Main results:
  • From the literature, the authors judged that asbestos accounted for 1% to 5% of U.S. lung cancer deaths. This range was an input to the method. Their other input ranges were 70% to 95% for smoking and 2% to 21% for radon.
  • The authors' own estimate was fewer than 5,560 occupational asbestos-related lung cancers in 2000, under 4% of the 155,600 U.S. lung cancer deaths that year. It was based on reported mesothelioma deaths and on the 7 to 3 ratio of lung cancer to mesothelioma claims in asbestos lawsuits.
  • The authors set the background lung cancer death rate (deaths without exposure to any carcinogen) at 3 per 100,000. The model counts these background deaths separately from the causal groups.
  • The method attributed between 0% and 3.2% of lung cancer deaths to the group of unspecified occupational and environmental pollutants other than smoking, radon and asbestos
  • Assuming 5% of the population was exposed to asbestos, the method gave relative-risk bounds for asbestos of 1.20 (lower) to 2.05 (upper)
• The authors' conclusion: The authors concluded that, if one is confident in the bounds given to the well-understood risk factors, the group of known and suspected lung carcinogens other than smoking, radon and asbestos together accounts for no more than 3.2% of total lung cancer mortality
• Limitations the authors state:
  • The input ranges came from the literature for illustration. The authors planned to gather expert opinion on the causes of lung cancer in future work.
  • Asbestos-related lung cancer could not be checked directly because such statistics are not collected
  • The lawsuit-based ratio used for the asbestos estimate is imperfect. Some mesotheliomas were not caused by asbestos, some lung cancers were probably due to smoking, and there was probably some diagnostic error.
  • The method assumes the total number of lung cancer deaths is known precisely, which the authors say is not strictly true
  • Exposure was treated as simply present or absent, which the authors acknowledge is not true
  • Only two-factor interactions involving cigarette smoke were considered, to simplify the analysis

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer.

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