Asbestos exposure, asbestosis, and asbestos-attributable lung cancer

Our plain-English summary of Asbestos exposure, asbestosis, and asbestos-attributable lung cancer, by R.N. Jones, J.M. Hughes, H. Weill (Thorax, 1996).

The study

• Authors: R.N. Jones, J.M. Hughes, H. Weill
• Journal: Thorax
• Published: 1996;51 Suppl 2(Suppl 2):S9-15
• Type of article: Review
• Cited by: 38 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Summary of the article

This review examined whether lung cancers attributable to asbestos are always associated with asbestosis (asbestos-induced lung fibrosis). The authors described this as a heated controversy with implications for regulation, workers' compensation and litigation. The review was written as a commentary on an introductory article, a case-control study by Wilkinson and colleagues (Lancet 1995), which reported an association between asbestos exposure and lung cancer in patients without radiographic small opacities. The authors traced the history of the evidence, from early case reports and Merewether's postmortem series to cohort studies of insulation and asbestos cement workers. They noted that Kipen et al found histological lung fibrosis in all 138 insulation workers with lung cancer who had acceptable tissue and radiographs. They also noted that Hughes and Weill found no excess lung cancer among asbestos cement workers without radiographic evidence of fibrosis. They criticised the Wilkinson study's exposure classification, its masking of radiographs and its dose-response findings, and judged that it did not provide convincing support for an asbestos-attributable risk in the absence of small opacities. They also reviewed evidence on lung fibrosis from other causes, registry studies, fibre burden studies, animal experiments, tumour site and cell type, and pleural plaques. They concluded that the issue was not settled, but that the weight of evidence strongly supported asbestosis as a necessary precursor. They stated that it was reasonable for judgements of attributability to rest on the presence of asbestosis diagnosed by radiography or histopathology.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This was a review article. It commented on a 1995 case-control study by Wilkinson and colleagues, which asked whether asbestos exposure is linked to lung cancer when chest X-rays show no signs of lung scarring (asbestosis). The authors criticised its methods, including how exposure was judged from job interviews and the masking of parts of the X-rays. They concluded that it did not give convincing support for an asbestos-related lung cancer risk without such signs. They also reviewed earlier research. In one cited series of insulation workers with lung cancer, all 138 cases with acceptable tissue and radiographs had lung scarring in tissue samples. A study of 839 asbestos cement workers by Hughes and Weill found no excess lung cancer, 20 or more years after hire, among workers without X-ray signs of scarring. The authors noted that lung scarring from other causes is also linked to raised lung cancer risk, and that pleural plaques had not proved a reliable risk marker. They concluded that the question was not settled, but that the weight of evidence strongly supported asbestosis as a necessary precursor of asbestos-attributable lung cancer.

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: Review and commentary on published studies, built around a critique of one case-control study (Wilkinson et al, Lancet 1995)
• Who was studied: No study population of its own. The authors reviewed published studies, centred on the Wilkinson et al case-control study, in which hospital patients with lung cancer were compared with hospital patients with other lung or heart disease
• Exposure: Asbestos exposure in general, examined in relation to asbestos-induced lung fibrosis (asbestosis) and lung cancer. Cited studies covered insulation workers, asbestos cement workers, South African amphibole asbestos miners, amosite and crocidolite lung fibre burdens, and crocidolite exposure
• Main results:
  • In the authors' assessment, the Wilkinson et al study did not convincingly show an asbestos-related lung cancer risk in people without small opacities (X-ray signs of fibrosis) on chest radiographs
  • As described by the authors, Wilkinson et al reported adjusted odds ratios of 2.03 (95% CI 1.00 to 4.13) for people with small opacities of profusion 1/0 or greater, and 1.56 (1.02 to 2.39) for those with 0/1 or 0/0. The second just reached statistical significance and the first just missed it
  • The authors pointed out that in the Wilkinson et al study, the crude odds ratio of 1.49 came from combining the 'definite' and 'probable' exposure categories. The 'definite' category alone would have given an odds ratio below 1.0
  • The authors argued that odds ratios in the Wilkinson et al study were higher for less than 10 years of exposure than for 10 or more years. In their view, this argued against a dose-response relationship in people with negative radiographs
  • In a cited 1987 series of insulation workers with lung cancer (Kipen et al), all 138 cases with acceptable tissue and radiographs had lung fibrosis in tissue samples, and 113 (82%) also had fibrosis on radiographs
  • In a cited prospective study of 839 men in two asbestos cement plants (Hughes and Weill), there was no excess lung cancer 20 or more years after hire among workers without radiographic fibrosis. Workers with small opacities of 1/0 or more had nine observed lung cancer deaths against 2.1 expected
  • In a cited necropsy series of 339 South African amphibole asbestos miners (Sluis-Cremer and Bezuidenhout), 24 of the 35 bronchial cancer cases had asbestosis. All 11 cases without asbestosis were smokers
  • The authors noted that lung fibrosis from many other causes is also associated with increased lung cancer risk
  • A cited Swedish study (Hillerdal, 1994) reported an adjusted risk ratio for lung cancer of 1.4 (95% CI 1.04 to 1.97) in men with pleural plaques but without radiographic asbestosis. The authors listed weaknesses of that study and concluded that pleural plaques have not proved a reliable marker of lung cancer risk
  • The authors stated that in animal inhalation experiments, excess lung tumours appeared only when lung fibrosis was also produced
• The authors' conclusion: The authors concluded that whether asbestosis is a necessary precursor of asbestos-attributable lung cancer was not settled, but that the weight of available evidence strongly supported it. In their view, it is reasonable for judgements of attributability to rest on the presence of asbestosis, diagnosed by radiography or histopathology
• Limitations the authors state:
  • The authors stated that the question cannot yet be considered settled
  • The authors noted that there are always reservations about applying animal data to humans, and that not all tumours in the animal studies were cancers
  • The authors stated that the case-control and fibre burden studies available so far were methodologically weak, with selection bias likely

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, Fibrosis, Case-Control Study, Asbestos-Cement, Insulator, Dose-response relationship, Attributable Risk.

Related studies

• Attributable risk: advantages of a broad definition of exposure — S. Wacholder, J. Benichou, et al. (1994)
• Occupational and non-occupational attributable risk of asbestos exposure for malignant pleural mesothelioma — A. Lacourt, C. Gramond, et al. (2014)
• The diagnosis of asbestosis — R.N. Jones (1991)
• Asbestosis as a precursor of asbestos related lung cancer: results of a prospective mortality study — J.M. Hughes, H. Weill (1991)
• Immunologic aberrations in asbestos cement workers: dissociation from asbestosis — R.D. deShazo, D.J. Hendrick, et al. (1983)
• Cohort mortality study of women compensated for asbestosis in Italy — D. Germani, S. Belli, et al. (1999)

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