Asbestosis, not asbestos exposure, is the primary risk factor for lung cancer

Our plain-English summary of Asbestosis, not asbestos exposure, is the primary risk factor for lung cancer, by R. Ross (American Journal of Respiratory and Critical Care Medicine, 2014).

The study

• Author: R. Ross
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 2014;189(1):114-5
• Type of article: Letter, Comment
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This was a letter to the editor, not a new study. The author re-examined figures from a 2013 study by Markowitz and colleagues of the North American insulator cohort. The author described these insulators as among the most heavily amphibole asbestos-exposed Americans alive. Using that study's Table 2, the author calculated that ever-smoking insulators with radiographic asbestosis around 1980 had a lung cancer rate ratio of 3.58 compared with ever-smokers in the Cancer Prevention Study II. For the 665 ever-smoking insulators without radiographic asbestosis, the ratio was 1.40. Years worked as an insulator were similar in the two groups. Based on deaths from asbestosis or other pulmonary fibrosis, the author estimated that about 12% of the group without asbestosis developed it later. Adjusting for this, the author estimated a rate ratio of about 1.10 for smoking insulators who never developed asbestosis. The author said the picture for nonsmokers was less clear because there were few deaths. The author concluded that asbestosis, not asbestos exposure, was the primary risk factor for lung cancer among smokers.

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: Letter to the editor (correspondence) re-analyzing published data from another study (Markowitz and colleagues, 2013)
• Who was studied: Insulators in the North American insulator cohort studied by Markowitz and colleagues, compared with ever-smokers in the Cancer Prevention Study II. The insulators were grouped by whether they had radiographic evidence of asbestosis around 1980. They included 665 ever-smoker insulators and 253 nonsmoking insulators without radiographic asbestosis.
• Exposure: Heavy amphibole asbestos exposure as insulators over many years, measured by duration of work as an insulator, together with cigarette smoking
• Main results:
  • Ever-smoker insulators with radiographic asbestosis around 1980, compared with Cancer Prevention Study II ever-smokers: the author calculated an adjusted lung cancer rate ratio of 36.79/10.29 = 3.58 from the Markowitz study's Table 2
  • The 665 ever-smoker insulators without radiographic asbestosis around 1980, compared with Cancer Prevention Study II ever-smokers: the author calculated an adjusted rate ratio of 14.44/10.31 = 1.40
  • Among current smokers without radiographic asbestosis (the Markowitz study's Figure 3), the author calculated a ratio of 27.7/19.1 = 1.45
  • Duration of work as an insulator was similar among smoking insulators with and without asbestosis (34.9 plus or minus 6.6 years versus 32.2 plus or minus 5.4 years)
  • In the group without asbestosis, 1.3% died from asbestosis or other pulmonary fibrosis, compared with 7.3% in the group with asbestosis. Using a background rate of about 0.5%, the author estimated that about 12% of insulators without asbestosis in the early 1980s developed asbestosis later.
  • After adjusting for the estimated 12% who later developed asbestosis, the author estimated a rate ratio of about 1.10 for smoking insulators who never developed asbestosis, which the author described as about the same as comparable smokers
  • Nonsmokers: there were only 7 lung cancer deaths among the 253 nonsmoking insulators without radiographic asbestosis, and the author said the picture for this group was less clear
• The authors' conclusion: The author concluded that among smokers without evidence of asbestosis, even with the heaviest exposure, any increased lung cancer risk is quite small and is not the primary risk factor. The author also concluded that if a person with lung cancer has evidence of asbestosis, asbestos was the primary cause.
• Limitations the authors state:
  • The author stated that the small number of lung cancer deaths among nonsmoking insulators without asbestosis (7 among 253) makes it difficult to quantify any increased risk in that group, and that some of them likely developed radiographic asbestosis later

Topics

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

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

Related studies

• The cigarette factor in asbestosis — W. Weiss (1990)
• Asbestos and smoking as risk factors for idiopathic retroperitoneal fibrosis: a case-control study — M. Goldoni, S. Bonini, et al. (2014)
• Risk factors for lung cancer in Iowa women: implications for prevention — J.S. Neuberger, J.D. Mahnken, et al. (2006)
• A Bayesian approach to assess interaction between known risk factors: the risk of lung cancer from exposure to asbestos and smoking — D. Wraith, K. Mengersen (2008)
• Asbestosis: a marker for the increased risk of lung cancer among workers exposed to asbestos — W. Weiss (1999)
• The effect of asbestosis on lung cancer risk beyond the dose related effect of asbestos alone — A. Reid, N. de Klerk, et al. (2005)

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