Significant relationship between the extent of pleural plaques and pulmonary asbestos body concentration in lung cancer patients with occupational asbestos exposure

Our plain-English summary of Significant relationship between the extent of pleural plaques and pulmonary asbestos body concentration in lung cancer patients with occupational asbestos exposure, by T. Yusa, K. Hiroshima, F. Sakai, et al (American Journal of Industrial Medicine, 2015).

The study

• Authors: T. Yusa, K. Hiroshima, F. Sakai, T. Kishimoto, K. Ohnishi, I. Usami, T. Morikawa, D. Wu, K. Itoi, K. Okamoto, Y. Shinohara, N. Kohyama, K. Morinaga
• Journal: American Journal of Industrial Medicine
• Published: 2015;58(4):444-55
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The aim of this study was to elucidate whether there is a relationship between the extent of pleural plaques and pulmonary asbestos body concentration (PABC).

Methods: The subjects were 207 lung cancer patients with occupational asbestos exposure. We determined the plaque extent by findings on chest images using our own criteria. PABCs were measured in resected or autopsy lung specimens.

Results: There was a significant relationship between plaque extent and PABC. Seventy-five percent of the patients determined to have extensive plaques based on our criteria had a PABC of ≥5,000 asbestos bodies per gram of dry lung tissue, which is one of the certification criteria of lung cancer caused by asbestos for workers' compensation in Japan.

Conclusions: In lung cancer patients, the plaque extent had a significant positive relationship with the PABC. The plaque extent would be useful as a proxy for PABC for lung cancer compensation purposes.

© 2015 Wiley Periodicals, Inc.

In plain English

This retrospective study at seven medical institutions in Japan looked at 207 lung cancer patients (204 men, 3 women) with definite or probable occupational asbestos exposure who had surgery or autopsy between 2003 and 2012. Two teams of specialists graded pleural plaques on chest X-rays and CT scans, and asbestos bodies were counted per gram of dry lung tissue. Japan's compensation system uses 5,000 or more bodies per gram as one criterion for lung cancer caused by asbestos. Patients with plaques on X-ray had a geometric mean of 25,061 bodies per gram, against 2,506 in those without. Of 81 patients the authors classed as having extensive plaques, 61 (75%) had 5,000 or more bodies per gram, compared with 30 of the other 126 (24%). A small number with extensive plaques had low counts, and many without them had high counts. The authors concluded that patients with extensive plaques are likely to meet the 5,000 criterion. They noted possible selection bias, unstandardized CT methods, and no data on asbestos fiber types.

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: Retrospective study of patients from multiple institutions, comparing pleural plaque extent on chest images with asbestos body counts in lung tissue
• Who was studied: 207 patients with primary lung cancer (204 men, 3 women; 159 surgical and 48 autopsy cases) treated at seven medical institutions in northern, central and western Japan, who had surgery or autopsy between 2003 and 2012; mean age 71.6 years
• Exposure: Occupational asbestos exposure, definite in 181 patients and probable in 26, in diverse jobs (most often construction sites, 67, and shipyards, 34). For the 200 patients with data, mean duration of exposure was 28.0 years and mean time since first exposure was 47.7 years. Fiber types were not recorded.
• Main results:
  • Agreement between the two specialist teams: 89.6% for the chest X-ray classification (kappa 0.72, 95% confidence interval 0.61 to 0.87) and 85.8% for the CT classification (kappa 0.69)
  • Geometric mean asbestos body concentration was 2,506 bodies per gram of dry lung in the 167 patients without plaques on chest X-ray and 25,061 in the 40 patients with plaques on chest X-ray; the difference was significant
  • Among the 40 patients with plaques on chest X-ray, 37 (93%) had 5,000 or more bodies per gram and 3 (8%) had fewer. Among the 167 without plaques on X-ray, 54 (32%) had 5,000 or more.
  • By CT class, the share with 5,000 or more bodies per gram was 13 of 76 (17%) in Class 0 (no plaques), 27 of 61 (44%) in Class 1 (plaques on less than a quarter of the inner chest wall) and 51 of 70 (73%) in Class 2 (a quarter or more)
  • Of 81 patients with 'extensive pleural plaques' (plaques on chest X-ray or CT Class 2), 61 (75%) had 5,000 or more bodies per gram of dry lung
  • Of the 126 patients without extensive plaques, 30 (24%) had 5,000 or more bodies per gram of dry lung
  • As an indicator of 5,000 or more bodies per gram, extensive plaques had a positive predictive value of 0.75 and a negative predictive value of 0.77
  • In multiple logistic regression, asbestos body concentration and time since first exposure significantly predicted plaques on chest X-ray. Only asbestos body concentration significantly predicted plaque extent on CT. Duration of exposure was not a significant predictor in either analysis.
  • A small number of patients with extensive plaques had low asbestos body counts
  • Many patients without extensive plaques had high asbestos body counts
• The authors' conclusion: The authors concluded that plaque extent had a significant relationship with asbestos body concentration. In their view, patients with extensive plaques by their imaging criteria are likely to have had cumulative exposure corresponding to 5,000 or more asbestos bodies per gram of dry lung, one of Japan's certification criteria for lung cancer caused by asbestos.
• Limitations the authors state:
  • Retrospective design, with possible selection bias because only surgery or autopsy cases were included
  • CT imaging methods were not standardized across institutions
  • Almost all subjects were men, so gender could not be analyzed
  • There was no information on asbestos types or fiber sizes, so chrysotile and amphibole exposure could not be compared. The authors also noted that chrysotile forms asbestos bodies less readily than amphiboles.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Asbestos Body Formation, Lung Cancer, Asbestos Exposure, Autopsy, Asbestos Bodies.

Related studies

• Relationship between number of asbestos bodies in autopsy lung and pleural plaques on chest X-ray film — T. Kishimoto, T. Ono, et al. (1989)
• The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan — T. Kishimoto, K. Morinaga, et al. (2000)
• Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis? — B. Clin, C. Paris, et al. (2011)
• Chest imaging and lung function impairment after long-term occupational exposure to low concentrations of chrysotile — D. Spyratos, D. Chloros, et al. (2012)
• Abnormal pulmonary function associated with diaphragmatic pleural plaques due to exposure to asbestos — K.H. Kilburn, R.H. Warshaw (1990)
• The natural course of lung function decline in asbestos exposed subjects with pleural plaques and asbestosis — M. Barnikel, P.M. Million, et al. (2019)

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