Asbestos-related pleural plaques and lung cancer

Our plain-English summary of Asbestos-related pleural plaques and lung cancer, by W. Weiss (Chest, 1993).

The study

• Author: W. Weiss
• Journal: Chest
• Published: 1993;103(6):1854-9
• Type of article: Review
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The English-language literature was reviewed to evaluate a possible relationship between asbestos-related pleural plaques and lung cancer in the absence of parenchymal asbestosis. There were six cohort studies in which the comparison group was limited to unexposed persons or the general population, four lung cancer case-control studies, and three autopsy studies. Of the 13 investigations, only 3 supported the hypothesis that lung cancer risk is elevated among persons with pleural plaques over the risk in unexposed people: 2 cohort studies from the same city in England with much the same data and 1 case-control study. These three studies had the most defects in design. The other ten studies failed to confirm the hypothesis. Thus, the weight of the evidence favors the conclusion that persons with asbestos-related pleural plaques do not have an increased risk of lung cancer in the absence of parenchymal asbestosis.

In plain English

This was a review of studies found through a literature search covering 1965 to mid-1992. It included foreign-language articles that had sufficiently informative English abstracts. It asked whether people with asbestos-related pleural plaques, but without asbestosis (diffuse scarring of the lung tissue), had a higher lung cancer risk than unexposed people or the general population. Thirteen studies qualified: six cohort, four case-control and three autopsy studies. Only three supported a raised risk: two cohort studies from Barrow, UK, which likely shared many subjects, and one case-control study. The author judged these three to have the most design defects. In four other cohort studies, relative risks ranged from 0.81 to 1.33, none statistically significant. Combined, those four studies observed 51 lung cancers against 50.4 expected (ratio 1.01, 95 percent confidence limits 0.75 to 1.33). The other three case-control studies were negative, and the autopsy studies showed slight, not statistically significant elevations. The author concluded that the weight of the evidence favors no increased lung cancer risk with plaques in the absence of asbestosis. The author also noted defects in all the studies and likely publication bias.

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 of cohort, case-control and autopsy studies, with the author's assessment of each study's methods. The literature search covered 1965 to mid-1992, and foreign-language articles with informative English abstracts were eligible.
• Who was studied: 13 published studies: six cohort studies whose comparison groups were unexposed people or the general population, four lung cancer case-control studies, and three autopsy studies. They came from the UK, Finland, Sweden, the US and Italy and were published between 1966 and 1992. One of them was published in Swedish.
• Exposure: Asbestos-related pleural plaques without asbestosis, used as a marker of asbestos exposure. The cohorts included shipyard workers, asbestos cement plant employees and people living near mines. Where specified, the fiber types were mixtures of chrysotile, amosite and crocidolite in two cohorts and mainly anthophyllite in one.
• Main results:
  • Of the 13 studies, only 3 supported a raised lung cancer risk in people with pleural plaques compared with unexposed people: 2 cohort studies from the same city in England and 1 case-control study.
  • In the Fletcher cohort study from Barrow (408 men with plaques), the standardized mortality ratio for lung cancer was 2.37 (p less than 0.005) in men with plaques. It was 1.25 (p = 0.52) in the control group. The reviewing author considered this study seriously flawed.
  • In the Edge study from Barrow, 19 of 429 men with plaques died of lung cancer, compared with 4 of 429 controls from Carlisle. Among the 407 men Edge kept for analysis, 8 of the 16 lung cancer deaths occurred in the first 2 years, which the reviewing author took as a sign of serious selection bias. From 2 years onward, the ratio of observed to expected lung cancer deaths was 1.19 (95 percent limits 0.51 to 2.35, calculated by the reviewing author).
  • In the four other cohort studies, none of the relative risks for lung cancer in people with plaques was statistically significantly different from 1.00. They ranged from 0.81 to 1.33, and the 1.33 figure was based on only 2 observed cases.
  • Summed across those four cohort studies, 51 lung cancers were observed and 50.4 were expected, a summary ratio of 1.01 with 95 percent Poisson confidence limits of 0.75 and 1.33.
  • Among the case-control studies, only the Hillerdal study (Sweden) showed a statistically significant raised odds ratio. Its numbers were not given and the odds ratio had to be estimated from a graph. The other three case-control studies had odds ratios of 0.75, 0.97 and 1.12, none statistically significant (p greater than 0.05).
  • In the three autopsy studies, the estimated relative risk was slightly raised in all three but not statistically significant in any. The figures were an odds ratio of 1.11, a relative risk of 1.51 (95 percent limits 0.75 to 3.09) and an odds ratio of 1.23.
  • Overall, 10 of the 13 studies were negative.
• The authors' conclusion: The author concluded that the weight of the evidence favors the view that people with asbestos-related pleural plaques do not have an increased risk of lung cancer in the absence of parenchymal asbestosis.
• Limitations the authors state:
  • All of the studies reviewed had defects of one kind or another.
  • None of the four case-control studies controlled for smoking.
  • Low autopsy rates in the autopsy studies allowed for significant bias.
  • Publication bias likely affected the literature reviewed.
  • A negative proposition is difficult to prove. The author called for a large unbiased study of an asbestos-exposed cohort with strictly defined plaques, compared with an unexposed cohort with good control of confounders.

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: Pleural Plaques, Lung Cancer, Autopsy, Case-Control Study.

Related studies

• Asbestos-related cancer risk in patients with asbestosis or pleural plaques — J. Ameille, P. Brochard, et al. (2011)
• Pleural plaque related to asbestos mining in Taiwan — H.Y. Yang, J.D. Wang, et al. (2010)
• Environmental asbestos-related pleural plaque in southeast of Turkey — G. Ates, T. Yildiz, et al. (2010)
• Absence of left-sided predominance in asbestos-related pleural plaques: a CT study — J.C. Gallego (1998)
• Asbestos-related pleural plaques and lung function — L.C. Oliver, E.A. Eisen, et al. (1988)
• Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis? — B. Clin, C. Paris, et al. (2011)

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