Lung cancer screening an asbestos exposed population: Existing lung cancer risk criteria are not sufficient

Our plain-English summary of Lung cancer screening an asbestos exposed population: Existing lung cancer risk criteria are not sufficient, by F.J.H. Brims, E.J.A. Harris, C. Murray, et al (Respirology, 2023).

The study

• Authors: F.J.H. Brims, E.J.A. Harris, C. Murray, C. Kumarasamy, A. Ho, B. Adler, P. Franklin, N.H. de Klerk
• Journal: Respirology
• Published: 2023;28(6):543-550
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background And Objective: Asbestos is a major risk factor for lung cancer, with or without tobacco smoke exposure. Low dose computed tomography (LDCT) screening for early lung cancer is effective but only when targeting high risk populations. This study aimed to analyse the effectiveness of LDCT screening in an asbestos exposed population and to compare lung cancer screening program (LCSP) eligibility criteria.

Methods: Participants in an asbestos health surveillance program, the Western Australia Asbestos Review Program, underwent at least one LDCT scan and lung function assessment as part of annual review between 2012 and 2017. Lung cancer cases were confirmed through linkage to the WA cancer registry. Theoretical eligibility for different screening programs was calculated.

Results: Five thousand seven hundred and two LDCT scans were performed on 1743 individuals. The median age was 69.8 years, 1481 (85.0%) were male and 1147 (65.8%) were ever-smokers (median pack-year exposure of 20.0). Overall, 26 lung cancers were detected (1.5% of the population; 3.5 cases per 1000 person-years of observation). Lung cancer was early stage in 86.4% and four (15.4%) cases were never smokers. Based on current lung screening program criteria, 1299 (74.5%) of this population, including the majority (17, 65.4%) of lung cancer cases, would not have been eligible for any LCSP.

Conclusion: This population is at raised risk despite modest tobacco exposure. LDCT screening is effective at identifying early-stage lung cancer in this population and existing lung cancer risk criteria do not capture this population adequately.

© 2023 The Authors. Respirology published by John Wiley & Sons Australia, Ltd on behalf of Asian Pacific Society of Respirology.

In plain English

This study looked at people in the Western Australia Asbestos Review Program, an annual health check for people with significant asbestos exposure, including former crocidolite miners, workers and residents of Wittenoom. Between 2012 and 2017, 1743 participants had 5702 low-dose CT scans; 85.0% were men and 65.8% had ever smoked. Twenty-six lung cancers were found (1.5% of participants; 3.5 cases per 1000 person-years). Of the 22 found on CT, 19 (86.4%) were early stage. Four of the 26 were in never smokers. The authors checked afterwards against US, Australian and UK screening rules. They found that 1299 participants (74.5%), and 17 of the 26 lung cancers (65.4%), would not have qualified under any of them, mainly because of limited smoking history. The authors concluded that this population is at raised risk despite modest smoking, that CT screening found early-stage cancer, and that existing risk criteria do not capture this population adequately. They noted that the numbers were too small to analyse independent risk factors and that overdiagnosis is possible.

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 cohort study of a health surveillance program using low-dose CT (LDCT), with a post-hoc (after the fact) analysis of theoretical eligibility under several lung cancer screening programs
• Who was studied: 1743 participants in the Western Australia Asbestos Review Program who had at least one LDCT scan, August 2012 to 2017, with nodule follow-up to August 2018. Median age 69.8 years, 1481 (85.0%) male, 1147 (65.8%) ever-smokers. Groups: 1155 with mixed-fibre exposure, 363 ex-Wittenoom residents and 225 Wittenoom workers.
• Exposure: Occupational and environmental asbestos exposure. The cohort began with crocidolite miners and workers and local township residents (Wittenoom). Other participants needed at least 3 months of cumulative asbestos exposure and/or pleural plaques or other asbestos-related disease on imaging (a mixed-occupation, mixed-fibre group). Median estimated cumulative exposure for the whole cohort was 0.7 fibre/mL years (IQR 0.1 to 3.0).
• Main results:
  • 26 lung cancers were identified over the study period in the whole cohort: 1.5% of the 1743 participants, a detection rate of 3.5 cases per 1000 person-years.
  • Of the 22 cancers detected on LDCT, 19 (86.4%) were stage IA or IB, one was stage IIA and two were stage IVA.
  • Four (15.4%) of the 26 lung cancer cases were in never smokers.
  • 1299 (74.5%) of the 1743 participants would not have been eligible for any of the screening programs examined, mainly because of their pack-years of smoking.
  • 17 (65.4%) of the 26 lung cancer cases would not have been eligible for any screening program.
  • Of the criteria examined, the authors judged the proposed UK program the best fit. In Table 5 it made 444 participants (25.5%) eligible and would have covered 9 (34.6%) of the 26 cancers. The Australian MSAC criteria were the least effective: 76 participants (4.4%) eligible, covering 2 (7.7%) of the cancers.
  • Compared with participants without lung cancer, those with lung cancer had greater tobacco smoke exposure, more emphysema on CT, and a higher median estimated cumulative asbestos exposure. However, the article's Table 3 gives p = 0.49 for the asbestos exposure difference (1.37 vs 0.72 fibre/mL years).
  • PLCOm2012 and LLP lung cancer risk scores appeared higher in the lung cancer cases, but the difference was not statistically significant.
  • 199 indeterminate lung nodules were found in 187 individuals. Of these nodules, 22 were diagnosed as lung cancer.
• The authors' conclusion: The authors concluded that this asbestos-exposed population is at raised lung cancer risk despite modest tobacco exposure, that LDCT screening is effective at identifying early-stage lung cancer in this population, and that existing lung cancer risk criteria do not capture this population adequately.
• Limitations the authors state:
  • The authors did not analyse independent risk factors for lung cancer or nodules (for example, with multivariate regression) because the numbers were small and results would likely be unreliable.
  • The predominance of adenocarcinomas found raises the likelihood of overdiagnosis.
  • The program was not designed as a lung cancer screening program but as health surveillance, so it had no upper age limit.
  • A formal cost-effectiveness evaluation has not been done.

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: Low-Dose CT Screening, Lung Cancer, Cancer Registry.

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• Predictive accuracy of the Liverpool Lung Project risk model for stratifying patients for computed tomography screening for lung cancer: a case-control and cohort validation study — O.Y. Raji, S.W. Duffy, et al. (2012)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• 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)
• Screening for lung cancer in a high-risk group: but I still haven't found what I'm looking for — G.A. Silvestri (2007)

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