Pleural plaques and the risk of pleural mesothelioma

Our plain-English summary of Pleural plaques and the risk of pleural mesothelioma, by J.C. Pairon, F. Laurent, M. Rinaldo, et al (Journal of the National Cancer Institute, 2013).

The study

• Authors: J.C. Pairon, F. Laurent, M. Rinaldo, B. Clin, P. Andujar, J. Ameille, P. Brochard, S. Chammings, G. Ferretti, F. Galateau-Sallé, A. Gislard, M. Letourneux, A. Luc, E. Schorlé, C. Paris
• Journal: Journal of the National Cancer Institute
• Published: 2013;105(4):293-301
• Cited by: 67 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The association between pleural plaques and pleural mesothelioma remains controversial. The present study was designed to examine the association between pleural plaques on computed tomography (CT) scan and the risk of pleural mesothelioma in a follow-up study of asbestos-exposed workers.

Methods: Retired or unemployed workers previously occupationally exposed to asbestos were invited to participate in a screening program for asbestos-related diseases, including CT scan, organized between October 2003 and December 2005 in four regions in France. Randomized, independent, double reading of CT scans by a panel of seven chest radiologists focused on benign asbestos-related abnormalities. A 7-year follow-up study was conducted in the 5287 male subjects for whom chest CT scan was available. Annual determination of the number of subjects eligible for free medical care because of pleural mesothelioma was carried out. Diagnosis certification was obtained from the French mesothelioma panel of pathologists. Survival regression based on the Cox model was used to estimate the risk of pleural mesothelioma associated with pleural plaques, with age as the main time variable and time-varying exposure variables, namely duration of exposure, time since first exposure, and cumulative exposure index to asbestos. All statistical tests were two-sided.

Results: A total of 17 incident cases of pleural mesothelioma were diagnosed. A statistically significant association was observed between mesothelioma and pleural plaques (unadjusted hazard ratio (HR) = 8.9, 95% confidence interval [CI] = 3.0 to 26.5; adjusted HR = 6.8, 95% CI = 2.2 to 21.4 after adjustment for time since first exposure and cumulative exposure index to asbestos).

Conclusion: The presence of pleural plaques may be an independent risk factor for pleural mesothelioma.

In plain English

This French follow-up study looked at 5287 retired or unemployed men who had been exposed to asbestos at work and had a chest CT scan in a screening program run between October 2003 and December 2005 in four regions of France. Expert chest radiologists read each scan for pleural plaques. New cases of pleural mesothelioma were found through national health insurance records up to March 31, 2011. Overall, 1078 men (20.4%) had parietal pleural plaques. Seventeen men developed pleural mesothelioma, and a pathology panel classed 14 of these as certain. A group of 802 men was compared with men without plaques; it combined men with typical parietal plaques (bilateral, thicker than 2 mm, more than 1 cm in extent) and men with diaphragmatic plaques. This group's unadjusted hazard ratio was 8.9 (95% CI 3.0 to 26.5). After accounting for cumulative exposure and time since first exposure, it was 6.8 (95% CI 2.2 to 21.4). Less typical plaques showed increased risks that were not statistically significant. The type of asbestos could not be determined. The authors concluded that pleural plaques may be an independent risk factor for pleural mesothelioma.

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: Follow-up (cohort) study of participants in a screening program, analyzed with Cox survival regression
• Who was studied: 5287 retired or unemployed men previously exposed to asbestos at work, who had a chest CT scan in the APEXS screening program between October 2003 and December 2005 in four regions of France (Aquitaine, Rhône-Alpes, Haute-Normandie, Basse-Normandie). Cancer follow-up ran to March 31, 2011.
• Exposure: Past occupational asbestos exposure, assessed by industrial hygienists from each man's work history and expressed as a cumulative exposure index in exposure units × years. The exposure of interest was pleural plaques seen on CT scan. The type of asbestos could not be determined.
• Main results:
  • 1078 of the 5287 men (20.4%) had parietal pleural plaques on CT scan, with or without diaphragmatic plaques. Another 20 men (0.4%) had isolated diaphragmatic plaques.
  • Of the 1098 men with pleural plaques, 782 (71.2%) had typical parietal plaques.
  • The group used in the hazard ratio comparisons combined typical parietal plaques with diaphragmatic plaques and contained 802 men.
  • 17 new cases of pleural mesothelioma were diagnosed during follow-up. 14 were classed as certain by the French mesothelioma pathology panel (MESOPATH). Of the 17 cases, 10 were in men with typical parietal or diaphragmatic plaques, 2 in men with less-typical plaques, and 5 in men without plaques on CT.
  • Compared with men without plaques, men with typical parietal or diaphragmatic pleural plaques had an unadjusted hazard ratio for pleural mesothelioma of 8.9 (95% CI 3.0 to 26.5).
  • After adjustment for time since first exposure and cumulative exposure index, the hazard ratio for typical parietal or diaphragmatic plaques was 6.8 (95% CI 2.2 to 21.4).
  • Less-typical plaques were linked to increased risks that were not statistically significant (unadjusted HR 4.9, 95% CI 0.9 to 25.5; adjusted HR 4.0, 95% CI 0.7 to 21.2).
  • When the analysis was limited to the 14 certified cases, the hazard ratio for typical parietal or diaphragmatic plaques was 6.5 (95% CI 2.0 to 20.8) crude and 4.9 (95% CI 1.5 to 16.6) adjusted.
  • Risk of pleural mesothelioma also increased with cumulative exposure index (HR 1.4, 95% CI 1.0 to 1.9, P = .06).
  • On review of tissue slides, 13 of the 17 mesothelioma cases had pleural plaques, including all five men who had no plaques on CT scan.
• The authors' conclusion: The authors concluded that the presence of pleural plaques may be an independent risk factor for pleural mesothelioma.
• Limitations the authors state:
  • The type of asbestos (chrysotile or amphiboles) and the asbestos load in mesothelioma cases could not be determined, partly because no autopsy was performed.
  • There were no air measurements and little detail on how often workers were exposed, so cumulative exposure was expressed in exposure units × years rather than fibers/mL × years.
  • The authors discussed whether an early mesothelioma could have been misread as a pleural plaque, and judged this highly improbable.
  • The authors discussed whether mesothelioma could have been detected differently in men with and without plaques, and judged this highly improbable.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Pleural Mesothelioma, CT Scan, Mesothelioma, Cumulative Exposure, Hazard Ratio, confidence interval.

Related studies

• Asbestos exposure, pleural plaques, and the risk of death from lung cancer — J.C. Pairon, P. Andujar, et al. (2014)
• Inter-reader agreement in HRCT detection of pleural plaques and asbestosis in participants with previous occupational exposure to asbestos — F. Laurent, C. Paris, et al. (2014)
• Asbestos exposure, pleural plaques and digestive cancers — B. Clin, C. Gramond, et al. (2025)
• Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis? — B. Clin, C. Paris, et al. (2011)
• Asbestos-related cancer risk in patients with asbestosis or pleural plaques — J. Ameille, P. Brochard, et al. (2011)
• Deep Learning for the Automatic Quantification of Pleural Plaques in Asbestos-Exposed Subjects — I. Benlala, B.D. De Senneville, et al. (2022)

Browse more research in Journal of the National Cancer Institute, or return to medical research.