Low-dose chest computed tomography screening of subjects exposed to asbestos

Our plain-English summary of Low-dose chest computed tomography screening of subjects exposed to asbestos, by K. Kato, K. Gemba, K. Ashizawa, et al (European Journal of Radiology, 2018).

The study

• Authors: K. Kato, K. Gemba, K. Ashizawa, H. Arakawa, S. Honda, N. Noguchi, S. Honda, N. Fujimoto, T. Kishimoto
• Journal: European Journal of Radiology
• Published: 2018;101:124-128
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: The primary aim was to reveal the prevalence of lung cancer (LC) and malignant pleural mesothelioma (MPM) in subjects with past asbestos exposure (AE). We also examined pulmonary or pleural changes correlated with the development of LC.

Materials And Methods: This was a prospective, multicenter, cross-sectional study. There were 2132 subjects enrolled between 2010 and 2012. They included 96.2% men and 3.8% women, with a mean age of 76.1 years; 78.8% former or current smokers; and 21.2% never smokers. We screened subjects using low-dose computed tomography (CT). The CT images were taken with a CT dose Index of 2.7 mGy. The evaluated CT findings included subpleural curvilinear shadow/subpleural dots, ground glass opacity or interlobular reticular opacity, traction bronchiectasia, honeycombing change, parenchymal band, emphysema changes, pleural effusion, diffuse pleural thickening, rounded atelectasis, pleural plaques (PQs), and tumor formation.

Results: The PQs were detected in most of subjects (89.4%) and emphysema changes were seen in 46.0%. Fibrotic changes were detected in 565 cases (26.5%). A pathological diagnosis of LC was confirmed in 45 cases (2.1%) and MPM was confirmed in 7 cases (0.3%). The prevalence of LC was 2.5% in patients with a smoking history, which was significantly higher than that in never smokers (0.7%, p = 0.027). The prevalence of LC was 2.8% in subjects with emphysema changes, which was higher than that of subjects without those findings (1.6%); although, the difference was not statistically significant (p = 0.056). The prevalence of LC in subjects with both fibrotic plus emphysema changes was 4.0%, which was significantly higher than that of subjects with neither of those findings (1.8%, p = 0.011). Logistic regression analysis revealed smoking history, fibrotic plus emphysema changes, and pleural effusion as significant explanatory variables.

Conclusions: Smoking history, fibrotic plus emphysema changes, and pleural effusion were correlated with the prevalence of LC.

Copyright © 2018 Elsevier B.V. All rights reserved.

In plain English

Researchers at eight Japanese hospitals screened 2132 people with past work-related asbestos exposure, enrolled 2010 to 2012, with one low-dose chest CT each. Most were men (2050), mean age 76.1 years; the largest job groups were shipbuilding, chemical manufacturing, asbestos-product manufacturing and construction. Scans showed pleural plaques in 89.4%, emphysema changes in 46.0% and fibrotic lung changes in 26.5%. Pathology confirmed lung cancer in 45 people (2.1%) and malignant pleural mesothelioma in 7 (0.3%). Lung cancer affected 2.5% with a smoking history versus 0.7% of never smokers. It was 4.0% with both emphysema and certain fibrotic changes (traction bronchiectasis, honeycombing or parenchymal bands) versus 1.8% in everyone else; the article's text calls that group 'neither', but its table includes people with one finding alone. Both differences were statistically significant. Lung cancer was about as common with plaques as without (2.1% vs 2.2%). In a combined analysis, smoking history, this combination, and fluid around the lung (pleural effusion) were statistically significant. The authors concluded these were correlated with lung cancer prevalence. They noted that cross-sectional data leave questions of cause to future prospective research.

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: Prospective, multicenter, cross-sectional screening study, with one low-dose chest CT scan per subject
• Who was studied: 2132 subjects with histories of occupational asbestos exposure, enrolled 2010 to 2012 at eight hospitals in Japan. There were 2050 men (96.2%) and 82 women (3.8%), with a mean age of 76.1 years (range 51 to 101). Of the 2095 with smoking data, 1651 (78.8%) were former or current smokers and 444 (21.2%) were never smokers.
• Exposure: Occupational asbestos exposure. Subjects qualified through more than 1 year in asbestos-product manufacturing, more than 10 years in other asbestos-related industries, or any asbestos-related work plus pleural plaques. The main job categories were shipbuilding (612, 28.7%), chemical manufacturing (260, 12.2%), asbestos-product manufacturing (259, 12.2%) and construction (245, 11.5%). Fiber types and doses were not reported.
• Main results:
  • Among all 2132 subjects, CT showed pleural plaques in 89.4% and emphysema changes in 46.0%.
  • Fibrotic lung changes, under the broad definition given in the text, were detected in 565 of the 2132 subjects (26.5%).
  • Lung cancer was confirmed by pathology in 45 subjects (2.1%), 44 men and 1 woman. Of these, 31 were adenocarcinoma, 10 squamous cell carcinoma, 3 small cell carcinoma and 1 adenosquamous carcinoma.
  • Malignant pleural mesothelioma was suspected in 16 subjects (0.8%) and confirmed by pathology in 7 (0.3%): 4 epithelioid, 2 biphasic and 1 sarcomatous.
  • Lung cancer prevalence was 2.5% (42 of 1651) in subjects with a smoking history, significantly higher than the 0.7% in never smokers (p = 0.027).
  • Lung cancer prevalence did not differ between subjects with and without pleural plaques (2.1% and 2.2%, p = 0.910).
  • Lung cancer prevalence was 2.8% in subjects with emphysema changes versus 1.6% without. This difference was not statistically significant (p = 0.056).
  • Lung cancer prevalence was 4.0% (13 of 328 in Table 2) in subjects with both emphysema changes and fibrotic changes. For this analysis, Table 2 defines fibrotic as traction bronchiectasis, honeycombing change, or parenchymal band. The comparison figure was 1.8% (32 of 1804, p = 0.011). The text calls that comparison group 'neither of those findings', but in Table 2 it is everyone without the combination, which includes people with only one of the findings.
  • Lung cancer prevalence was significantly higher in the 45 subjects with pleural effusion (Table 2: 7 of 45 with lung cancer, versus 38 of 2087 without effusion; p less than 0.001). Of the effusion cases described in the text, three subjects with lung cancer had undergone thoracic surgery, which the authors suggested meant post-operative effusion.
  • In logistic regression, the authors reported smoking history, fibrotic plus emphysema changes, and pleural effusion all as statistically significant. Table 3 prints: pleural effusion 10.238 (95% CI 4.221 to 24.833, p less than 0.001); fibrotic plus emphysema changes 1.954 (95% CI 0.999 to 3.824, p = 0.050); smoking 0.270 (95% CI 0.082 to 0.891, p = 0.032).
• The authors' conclusion: The authors concluded that smoking history, fibrotic plus emphysema changes, and pleural effusion were correlated with the prevalence of lung cancer. They called for future studies on whether low-dose CT screening of asbestos-exposed people improves lung cancer prognosis.
• Limitations the authors state:
  • The study is cross-sectional. The suggested causal links between lung cancer and some CT findings need to be clarified in a future prospective study.
  • Each subject had only one CT scan, and subjects with a negative CT were not followed up.
  • Because many subjects smoked, it is unclear whether the slight fibrotic changes were specific to asbestos exposure or due to other causes such as smoking.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Pleural Mesothelioma, Asbestos Exposure, Low-Dose CT Screening, Subpleural Curvilinear Line, Honeycombing, Emphysema, Pleural Effusion.

Related studies

• Diagnostic Performance of Ultra-Low-Dose Computed Tomography for Detecting Asbestos-Related Pleuropulmonary Diseases: Prospective Study in a Screening Setting — M. Schaal, F. Severac, et al. (2016)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• Low-dose computed tomography (LDCT) in workers previously exposed to asbestos: detection of parenchymal lung disease — M.C. Carrillo, S. Alturkistany, et al. (2013)
• Impact of low-dose computed tomography screening on lung cancer mortality among asbestos-exposed workers — F. Barbone, F. Barbiero, et al. (2018)
• Low-voltage chest CT: another way to reduce the radiation dose in asbestos-exposed patients — D. Macía-Suárez, E. Sánchez-Rodríguez, et al. (2017)
• Screening of miners and millers at decreasing levels of asbestos exposure: comparison of chest radiography and thin-section computed tomography — M. Terra-Filho, E. Bagatin, et al. (2015)

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