Screening for malignant pleural mesothelioma and lung cancer in individuals with a history of asbestos exposure

Our plain-English summary of Screening for malignant pleural mesothelioma and lung cancer in individuals with a history of asbestos exposure, by H.C. Roberts, D.A. Patsios, N.S. Paul, et al (Journal of Thoracic Oncology, 2009).

The study

• Authors: H.C. Roberts, D.A. Patsios, N.S. Paul, M. DePerrot, W. Teel, H. Bayanati, F. Shepherd, M.R. Johnston
• Journal: Journal of Thoracic Oncology
• Published: 2009;4(5):620-8
• Cited by: 60 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: We established a screening program for prior asbestos workers using low-dose computed tomography (LDCT).

Methods: Between March 2005 and October 2007 we performed LDCT (50-60 mA, 120 kV, 1.25 mm) in 516 asbestos-exposed individuals. Parenchymal nodules were followed according to lung cancer screening recommendations, morphology and location of pleural plaques was noted in detail.

Results: We included 507 men and 9 women (median 60.0 years), 395 (76.6%) were smokers. Annual repeat has been performed in 356 participants. We found plaques in 357 subjects (69.2%), commonly calcified (79.6%), flat (86.6%), and symmetric (86.8%), and mostly involving the costal (96.4%) and diaphragmatic (81.8%) pleura. Uncommon plaques were lobulated (13.2%), right-dominant asymmetric (4.5%), or with effusions (0.1%).We found pulmonary nodules in 371 subjects (71.9%), 91 (17.6%) had at least one nodule > or =5 mm; 10 growing nodules were found on annual repeat LDCT. In 41 individuals, plaques were regarded as atypical; three had new pleural/peritoneal abnormalities on annual repeat LDCT. An interim limited computed tomography of the observed abnormality prompted 10 diagnostic biopsies, resulting in a diagnosis of six lung cancers, two pleural mesothelioma and two peritoneal mesothelioma; overall rate of screen-detected malignancies is 2.1%. There were four interval cancers, diagnosed after baseline (n = 1) or after the annual repeat (n = 3): two pleural and one peritoneal mesothelioma, and one mixed squamous/small cell carcinoma.

Conclusion: Screening prior asbestos workers detects advanced malignant pleural mesothelioma and early as well as late stage lung cancer. We expect to learn more about the appearance of "early mesothelioma" with continued screening.

In plain English

This study reported on a low-dose chest CT screening program in Ontario, Canada, for 516 people with past asbestos exposure (507 men and 9 women, median age 60). They were scanned between March 2005 and October 2007, and 356 had also had an annual repeat scan. Pleural plaques were seen in 357 people (69.2%), and 41 (7.9%) had plaques the authors judged atypical. Lung nodules were seen in 371 people (71.9%). Screening led to the diagnosis of six lung cancers, two malignant pleural mesotheliomas and two malignant peritoneal mesotheliomas, an overall malignancy rate the authors gave as 2.1%. Four more cancers, three of them mesotheliomas, were diagnosed between scheduled screens. All mesothelioma patients died soon after diagnosis, and the longest survival was 9 months. The authors found no CT feature that predicted mesothelioma, and screening did not lead to early diagnosis of mesothelioma in any case. The authors concluded that screening detected advanced mesothelioma and early as well as late stage lung cancer. They named a short observation period as a limitation.

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: Screening program (prospective screening study) using low-dose computed tomography (LDCT), with a baseline scan, short-term follow-up scans of suspicious findings, and annual repeat scans
• Who was studied: 516 asbestos-exposed individuals (507 men, 9 women; median age 60, range 32 to 83) enrolled in Ontario, Canada, between March 2005 and October 2007. Of these, 338 were recruited through the Occupational Health Clinics for Ontario Workers in Sarnia-Lambton and 178 were referred by workers' unions and other contacts. There were 104 current smokers, 291 former smokers and 121 never smokers. 356 had had their annual repeat CT at the time of analysis.
• Exposure: Asbestos exposure at least 20 years earlier, or documented pleural plaques. Exposure was documented in 510 people (98.8%); six were enrolled on the basis of pleural plaques alone. The fiber type was reported as unknown (230), all (16), or a mixture of different asbestos types (66), mostly amphiboles (19), chrysotiles (84), crocidolites (12), or asbestos in blue mud cement (89).
• Main results:
  • At baseline, 357 of the 516 participants (69.2%) had at least mild pleural plaques. Plaques most often involved the costal pleura (344, 96.4% of 357), then the diaphragmatic pleura (292, 81.8%) and the mediastinal pleura (107, 30.0%).
  • Among the 357 people with plaques, all plaques were flat in 309 (86.6%), and 47 (13.2%) had at least one lobulated plaque.
  • 41 individuals (7.9%) were considered to have atypical pleural plaques at baseline.
  • One or more lung nodules were found in 371 individuals (71.9%). In 91 (17.6%), at least one nodule was 5 mm or larger and needed a follow-up scan.
  • Invasive procedures were recommended from baseline scans in 10 of 516 participants (1.9%), and 7 of these revealed malignancy. From annual scans, 4 of 356 (1.1%) had invasive procedures, and 3 revealed malignancy.
  • Screen-detected cancers were six lung cancers, two malignant pleural mesotheliomas and two malignant peritoneal mesotheliomas (seven found at baseline, three on annual scans), for an overall malignancy rate the authors gave as 2.1%.
  • Four interval cancers were diagnosed after baseline (1) or after the annual repeat (3): two pleural mesotheliomas, one peritoneal mesothelioma, and one squamous cell carcinoma with a small cell carcinoma focus in a lymph node.
  • Three screen-detected lung cancers were stage 1 non-small cell lung cancer (one squamous cell carcinoma, two adenocarcinomas), and one was small cell carcinoma.
  • All malignancies were found in smokers, who had an average 31 pack-year history.
  • All mesothelioma patients died soon after diagnosis. The maximum survival was 9 months.
  • The authors could not identify any single CT feature or combination of CT changes that predicted malignant pleural mesothelioma in the patients who developed it after their first screening scan.
• The authors' conclusion: The authors concluded that screening prior asbestos workers detects advanced malignant pleural mesothelioma and early as well as late stage lung cancer. They stated that whether LDCT will lead to diagnosis of an 'early' mesothelioma that can be treated with curative intent still has to be addressed, and that they expect to learn more about 'early mesothelioma' with continued screening.
• Limitations the authors state:
  • Short observation period
  • Magnetic resonance imaging, which may help tell plaques from mesothelioma, was not used because of limited availability and high expense

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Lung Cancer, Asbestos Exposure, Low-Dose CT Screening, Pleural Plaques, Pleura, Peritoneal Mesothelioma, Carcinoma.

Related studies

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• Asbestos Surveillance Program Aachen (ASPA): initial results from baseline screening for lung cancer in asbestos-exposed high-risk individuals using low-dose multidetector-row CT — M. Das, G. Mühlenbruch, et al. (2007)
• Yield of Low-Dose Computerized Tomography Screening for Lung Cancer in High-Risk Workers: The Case of 7189 US Nuclear Weapons Workers — S.B. Markowitz, A. Manowitz, et al. (2018)
• Comparison of lung asbestos fiber content in cancer subjects with healthy individuals with no known history of occupational asbestos exposure in Korea — J.H. Han, J.D. Park, et al. (2009)
• Resected Lung Cancer Patients Who Would and Would Not Have Met Screening Criteria — F. Farjah, D.E. Wood, et al. (2016)
• Psychological impact of computed tomography screening for lung cancer and occupational pulmonary disease among asbestos-exposed workers — T. Vierikko, S. Kivistö, et al. (2009)

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