Ultra low dose CT screen-detected non-malignant incidental findings in the Western Australian Asbestos Review Programme

Our plain-English summary of Ultra low dose CT screen-detected non-malignant incidental findings in the Western Australian Asbestos Review Programme, by C.P. Murray, P.M. Wong, J. Teh, et al (Respirology, 2016).

The study

• Authors: C.P. Murray, P.M. Wong, J. Teh, N. de Klerk, T. Rosenow, H. Alfonso, A. Reid, P. Franklin, A.W. Musk, F.J. Brims
• Journal: Respirology
• Published: 2016;21(8):1419-1424
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background And Objective: Computed tomography (CT)-based studies of asbestos-exposed individuals report a high prevalence of lung cancer, but the utility of low dose CT (LDCT) to screen asbestos-exposed populations is not established. We aimed to describe the prevalence of indeterminate pulmonary nodules and incidental findings on chest LDCT of asbestos-exposed subjects in Western Australia.

Methods: A total of 906 subjects from the Western Australian Asbestos Review Programme underwent LDCT of the chest as part of regular annual review. An indeterminate (solid) nodule was defined as >50 mm3 and part-solid/non-solid nodules >5 mm. The presence of asbestos-related diseases was recorded with a standardized report.

Results: Subjects were mostly (81%) men with a median age of 70 years. Fifty-eight (6.5%) participants were current smokers, 511 (56.4%) ex-smokers and 325 (36.4%) never-smokers. One hundred and four indeterminate nodules were detected in 77 subjects (8.5%); of these, eight cases had confirmed lung cancer (0.88%). Eighty-seven subjects (9.6%) had incidental findings that required further investigation, 42 (4.6%) from lower airways inflammation. The majority of nodules were solid, 4-6 mm and more common with age. Five hundred and eighty (64%) subjects had pleural plaques, and 364 (40.2%) had evidence of interstitial lung disease.

Conclusion: The prevalence of LDCT-detected indeterminate lung nodules in 906 individuals with significant asbestos exposure was 8.5%, lower than many other CT studies. Clinically important incidental findings were found in 9.4%, predominantly related to lower respiratory tract inflammation. LDCT appears to effectively describe asbestos-related diseases and is likely to be an acceptable modality to monitor asbestos-exposed individuals.

© 2016 Asian Pacific Society of Respirology.

In plain English

This study reported what ultra low dose chest CT scans showed in 906 of 1308 members of the Western Australian Asbestos Review Programme, scanned between September 2012 and August 2013. Members included former workers and ex-residents of Wittenoom, where crocidolite was mined and milled, and other asbestos-exposed workers. Indeterminate (possibly significant) lung nodules were found in 77 people (8.5%), and eight people (0.88%) had lung cancer confirmed by tissue examination. Other findings needing further evaluation were seen in 85 people (9.4%), most often lower respiratory tract inflammation (42 people, 4.6%). Four of these people had malignant mesothelioma. Parietal pleural plaques were present in 580 people (64.0%). Interstitial lung disease was judged definite in 232 (25.7%) and probable in 132 (14.6%). The number of nodules did not correlate with pack years of smoking or cumulative asbestos exposure. The authors concluded that this kind of CT appears acceptable for monitoring asbestos-exposed people, but that lung cancer risk needs better definition before widespread use. The authors noted that about 80% of participants had earlier chest X-rays, which might have caused selection 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: Report of first-round ultra low dose CT screening findings within a prospective cohort (an ongoing clinical review programme)
• Who was studied: 906 of 1308 (69.3%) Asbestos Review Programme participants in Western Australia who chose to have low dose CT between 1 September 2012 and 31 August 2013
• Exposure: Former workers of the Wittenoom crocidolite mine and mill, former residents of Wittenoom town, and other workers with more than 3 months of full-time-equivalent occupational asbestos exposure and/or pleural plaques
• Main results:
  • Among the 337 people from Wittenoom with exposure measurements, the median cumulative asbestos exposure was 4.20 fibre/ml-years (interquartile range 1.38 to 9.93)
  • 104 indeterminate nodules were found in 77 of the 906 participants (8.5%), and all had further follow-up
  • Most indeterminate nodules were solid (72, or 69.2%)
  • The number of nodules did not correlate with pack years of smoking (P=0.840), time since quitting (P=0.789), age (P=0.431) or cumulative asbestos exposure (P=0.319)
  • Eight participants (0.88%) had histologically confirmed lung cancer
  • 85 participants (9.4%) had incidental findings of potential clinical significance; the most common was lower respiratory tract inflammation, in 42 (4.6%)
  • Malignant mesothelioma was diagnosed in four participants, none of whom had symptoms at the time
  • Parietal pleural plaque was present in 580 participants (64.0%), of which 512 (88.3%) were calcified
  • The pleural plaque score rose by 0.074 (95% CI 0.048 to 0.099) for each one-unit increase in cumulative exposure in fibre/ml-years
  • Interstitial lung disease was judged definite in 232 (25.7%) and probable in a further 132 (14.6%) participants
  • 162 participants (17.8%) were recalled for further investigation because of nodules or other incidental findings
  • Four participants had a small collapsed lung caused by the CT-guided biopsy; none needed treatment for it
• The authors' conclusion: The authors concluded that low dose CT appears to be an acceptable way to monitor asbestos-exposed individuals, but that the level of lung cancer risk needs to be better defined before widespread adoption
• Limitations the authors state:
  • About 80% of participants had a chest X-ray at least 1 year before the CT, possibly creating selection bias
  • Each initial scan was read by one of two thoracic radiologists
  • Ultra low dose CT has not been established as a valid substitute for standard dose or high resolution CT in diagnosing asbestos-related abnormalities

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: Lung Cancer, Inflammation, Pleural Plaques, Interstitial Lung Disease, Asbestos Exposure.

Related studies

• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• Correlation of ultra-low dose chest CT findings with physiologic measures of asbestosis — D. Manners, P. Wong, et al. (2017)
• Correlation of lung function with ultra-low-dose CT-detected lung parenchymal abnormalities: a cohort study of 1344 asbestos exposed individuals — F. Brims, E.J. Harris, et al. (2022)
• Asbestos-related pleural disease in Western Australian gold-miners — Y.C. Lee, N.H. De Klerk, et al. (1999)
• Fibrolipoma of the left ventricle: an uncommon incidental autopsy finding — K. Fragkouli, A. Mitselou, et al. (2020)
• Erionite in road gravel associated with interstitial and pleural changes--an occupational hazard in western United States — P.H. Ryan, M. Dihle, et al. (2011)

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