Asbestosis and lobar site of lung cancer

Our plain-English summary of Asbestosis and lobar site of lung cancer, by W. Weiss (Occupational and Environmental Medicine, 2000).

The study

• Author: W. Weiss
• Journal: Occupational and Environmental Medicine
• Published: 2000;57(5):358-60
• Type of article: Review
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To assess the evidence for the hypothesis that lung cancer has a predilection for the lower lobes in workers with asbestosis.

Method: A review of the available literature with relevant information.

Results: Six published reports were analysed. In four studies limited to series of cases with diagnoses of asbestosis, three showed lower lobe predominance of lung cancer whereas the fourth study included cases in which the radiographic readings did not meet the usual criterion of profusion for asbestosis. One cohort study showed lower lobe predominance; the other reported only 33% lower lobe cancers compared with 20% in unexposed controls.

Conclusion: There is some support for the hypothesis but more studies are needed.

In plain English

This short report reviewed published studies on whether lung cancer tends to start in the lower lobes in workers with asbestosis. The author found twelve studies and analysed six. Six mostly autopsy or surgical case collections were excluded for selection bias. In three of four case series of lung cancer with asbestosis, 62.5% to 88.3% of cancers were in the lower lobes. The fourth series, which included cases with X-ray readings below the usual asbestosis threshold, reported 35.3%. In a Dresden cohort (1952–64), counting only upper- and lower-lobe cancers, 68.8% among workers with asbestosis were in the lower lobes, compared with 28.6% in the city's general population. A later cohort of 4060 asbestos workers (1985–96) used the same upper-plus-lower-lobe count. It found 32.9% in the lower lobes, with no rise by degree of asbestosis. The figure among heavy-smoker controls was 20.4%, a statistically significant difference. The author noted that there were few studies, that methods varied, and that asbestos exposure declined over the period covered. The author concluded there was some support for the hypothesis but more studies were needed.

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: Literature review (short report) of published studies on the lobe of origin of lung cancer in people with asbestosis, found through Medline and bibliographies of English-language papers
• Who was studied: Twelve studies were found. Six were analysed: four case series of lung cancer in people said to have asbestosis (published 1966–1978, cases collected before 1977, 17 to 65 cases each) and two cohorts of asbestos workers. The cohorts were 2636 Dresden workers (1952–64) and 4060 asbestos workers compared with 14 254 heavy cigarette smokers (1985–96). Six autopsy or surgical case collections were excluded for selection bias.
• Exposure: Asbestos exposure, with asbestosis diagnosed or graded by chest X-ray (profusion of small irregular opacities). No fiber types are specified.
• Main results:
  • In the four case series of lung cancer with asbestosis, the share of cancers in the lower lobes ranged from 62.5% to 88.3% in the first three studies. It was 35.3% in the fourth (Huuskonen) study.
  • The fourth case series included cases whose X-ray readings did not meet the usual profusion criterion for asbestosis. The author suggested this may explain the discrepancy.
  • In the Dresden cohort (Jacob and Anspach), 68.8% of lung cancers among workers with asbestosis originated in the lower lobes, compared with 28.6% in the general population. Both percentages used cancers in the upper and lower lobes combined as the denominator.
  • In the Dresden cohort, lung cancer risk was increased only among workers with asbestosis, compared with the general population, after adjustment for age and sex.
  • In the Brodkin et al cohort (73 lung cancers among asbestos workers), lower lobe cancers were 31%, 35% and 33% across increasing X-ray profusion groups, and 32.9% overall.
  • For the Brodkin et al cohort, as for the Dresden cohort, the table gives the denominator for the lower lobe percentage as upper- plus lower-lobe cancers.
  • In the Brodkin et al cohort, the author found no predilection for lower lobe location among asbestos workers at any degree of asbestosis.
  • In the Brodkin et al study, 20.4% of lung cancers among the heavy-smoker controls were in the lower lobes. The difference from the 32.9% in asbestos workers was statistically significant (p less than 0.05).
  • The Brodkin et al study's authors calculated an odds ratio of 1.92 (95% CI 1.03 to 3.55) for lower lobe cancer in asbestos workers compared with controls.
• The authors' conclusion: The author concluded that there is some support for the hypothesis that lung cancer favours the lower lobes in people with asbestosis, but that the information is limited and more studies with good epidemiological design are needed.
• Limitations the authors state:
  • Few studies were available.
  • The source of material was seldom population based and often poorly defined.
  • The method for diagnosing asbestosis varied between studies.
  • The studies spanned an era with a marked decline in asbestos exposure.
  • In the Brodkin et al study, the chest X-ray was taken up to 10 years (mean 4 years) before the lung cancer diagnosis. Asbestosis could have developed or progressed in that interval.
  • The two cohorts used different X-ray classification systems that cannot be equated.
  • The Dresden study gave no information on how the lobe of origin was assessed.

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: Lung Cancer, Cohort Study.

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