Cancer mortality in a surveillance cohort of German males formerly exposed to asbestos

Our plain-English summary of Cancer mortality in a surveillance cohort of German males formerly exposed to asbestos, by B. Pesch, D. Taeger, G. Johnen, et al (International Journal of Hygiene and Environmental Health, 2010).

The study

• Authors: B. Pesch, D. Taeger, G. Johnen, I.M. Gross, D.G. Weber, M. Gube, A. Müller-Lux, E. Heinze, T. Wiethege, V. Neumann, A. Tannapfel, H.J. Raithel, T. Brüning, T. Kraus
• Journal: International Journal of Hygiene and Environmental Health
• Published: 2010;213(1):44-51
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The objective of this analysis was the estimation of the cancer risks of asbestos and asbestosis in a surveillance cohort of high-exposed German workers. A group of 576 asbestos workers was selected for high-resolution computer tomography of the chest in 1993-1997. A mortality follow-up was conducted through 2007. Standardised mortality ratios (SMRs) were calculated and Poisson regression was performed to assess mesothelioma risks. A high risk was observed for pleural mesothelioma (SMR 28.10, 95% CI 15.73-46.36) that decreased after cessation of exposure (RR 0.1; 95% CI 0.0-0.6 for > or =30 vs. <30 years after last exposure). Asbestosis was a significant risk factor for mesothelioma (RR 6.0, 95% CI 2.4-14.7). Mesothelioma mortality was still in excess in former asbestos workers although decreasing after cessation of exposure. Fibrosis was associated with subsequent malignancy.

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In plain English

This prospective cohort study followed 576 highly asbestos-exposed German men. They joined a high-resolution chest CT surveillance program in 1993-1997. Most had been exposed to chrysotile. Through April 30, 2007, 128 men died. Compared with German men in general, overall deaths were lower than expected (SMR 0.59, 95% CI 0.49-0.70). However, 15 men died of pleural mesothelioma where 0.53 deaths were expected (SMR 28.10, 95% CI 15.73-46.36). Lung cancer deaths (8) were below expectation (SMR 0.39, 95% CI 0.17-0.77). Within the group, men with a recognized asbestos-related occupational disease (asbestosis and pleural thickenings) had a higher mesothelioma risk (RR 6.0, 95% CI 2.4-14.7). Lung fibrosis seen on CT was associated with later lung cancer (RR 3.1, 95% CI 1.1-9.0). Mesothelioma risk was lower 30 or more years after last exposure than under 30 years (RR 0.1, 95% CI 0.0-0.6). Estimated fibre-years did not show a clear dose-response pattern. The authors concluded that mesothelioma mortality stayed high after the asbestos ban but decreased with time since exposure ended. They named low participation and categorical exposure estimates as limitations.

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: Prospective surveillance cohort with mortality follow-up; comparison with German male mortality (standardised mortality ratios) and internal comparisons by Poisson regression
• Who was studied: 576 German males among 636 workers (response rate 33.2%) who took part in an extended HRCT surveillance program for highly asbestos-exposed workers, 1993-1997; median age at baseline 63 years (range 53-70); followed to April 30, 2007
• Exposure: Occupational asbestos exposure, mostly chrysotile (crocidolite less often and usually with other forms), in insulation, asbestos cement applications, and the manufacture of friction pads or textiles; about 50% had 25 or more fibre years; average exposure duration 20 years; median first exposure 1950, median last exposure 1971
• Main results:
  • Whole cohort: overall mortality was lower than expected compared with German males (SMR 0.59; 95% CI 0.49-0.70)
  • Whole cohort: 15 deaths from pleural mesothelioma versus 0.53 expected (SMR 28.10, 95% CI 15.73-46.36)
  • Whole cohort: 8 deaths from lung cancer, below expected (SMR 0.39, 95% CI 0.17-0.77)
  • Internal comparison: recognized asbestos-related occupational disease (asbestosis and pleural thickenings), present in 13 of the 15 mesothelioma cases, was associated with a significant mesothelioma risk (RR 6.0; 95% CI 2.4-14.7)
  • Internal comparison: pleural thickenings and plaques on HRCT at baseline were linked to a non-significantly increased mesothelioma risk (RR 2.1, 95% CI 0.9-4.9)
  • Mesothelioma risk declined significantly with time since last exposure (RR 0.1, 95% CI 0.0-0.6 for 30 or more years versus less than 30 years)
  • Cumulative exposure in fibre years did not show a clear dose-response effect; for mesothelioma, RR 0.8 (95% CI 0.4-1.8) for more than 50 versus less than 25 fibre years
  • Smoking was not associated with a significant mesothelioma risk (RR 1.2; 95% CI 0.5-2.8)
  • Internal comparison based on 8 lung cancer cases: fibrotic lung alterations on HRCT at baseline were associated with subsequent lung cancer (RR 3.1, 95% CI 1.1-9.0)
• The authors' conclusion: The authors concluded that mesothelioma mortality in formerly high-exposed workers was still high after the asbestos ban but decreased with time since exposure ended in the long term. They also concluded that fibrotic alterations of the pleura and lung were predictors of pleural mesothelioma and lung cancer.
• Limitations the authors state:
  • Low participation rate in the voluntary program
  • Asbestos exposure at baseline was assessed only in categories
  • Because the analysis was based on high-exposed cases, variation in exposure levels may have been too limited to assess dose-response relations
  • Selection of health-interested subjects with many former smokers must be considered when interpreting the lung cancer risk; all lung cancer cases were smokers, which impaired the internal comparison
  • The high average age at enrolment might indicate a healthy survivor effect
  • Death certificates are of limited quality (one mesothelioma was missing from a death certificate, another was recorded as lung cancer in the register)
  • Because of the small cohort and exposure uncertainties, data were not analysed by asbestos type

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pleural Mesothelioma, Fibrosis.

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