Lung Cancer Screening in Asbestos-Exposed Populations

Our plain-English summary of Lung Cancer Screening in Asbestos-Exposed Populations, by S.B. Markowitz (International Journal of Environmental Research and Public Health, 2022).

The study

• Author: S.B. Markowitz
• Journal: International Journal of Environmental Research and Public Health
• Published: 2022;19(5)
• Type of article: Review
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos exposure is the most important cause of occupational lung cancer mortality. Two large randomized clinical trials in the U.S. and Europe conclusively demonstrate that annual low-dose chest CT (LDCT) scan screening reduces lung cancer mortality. Age and smoking are the chief risk factors tested in LDCT studies, but numerous risk prediction models that incorporate additional lung cancer risk factors have shown excellent performance. The studies of LDCT in asbestos-exposed populations shows favorable results but are variable in design and limited in size and generalizability. Outstanding questions include how to: (1) identify workers appropriate for screening, (2) organize screening programs, (3) inform and motivate people to screen, and (4) incorporate asbestos exposure into LDCT decision-making in clinical practice. Conclusion: Screening workers aged ≥50 years with a history of ≥5 years asbestos exposure (or fewer years given intense exposure) in combination with either (a) a history of smoking at least 10 pack-years with no limit on time since quitting, or (b) a history of asbestos-related fibrosis, chronic lung disease, family history of lung cancer, personal history of cancer, or exposure to multiple workplace lung carcinogens is a reasonable approach to LDCT eligibility, given current knowledge. The promotion of LDCT-based screening among asbestos-exposed workers is an urgent priority.

In plain English

This single-author review covered low-dose CT lung cancer screening in asbestos-exposed people. It was not a full systematic review. It identified nine non-randomized studies (2002 to 2019), each with at least 150 participants. Combined, these detected 86 lung cancers among 5548 ever smokers (1.55%) and 6 among 1787 never smokers (0.33%). Only one, in Northeastern Italy, followed deaths: its CT-screened group had a lung cancer hazard ratio of 0.41 (95% CI 0.17 to 0.96) versus a chest X-ray group, but the groups were not randomized and differed in risk factors. The author noted no randomized trials existed in asbestos-exposed groups and studies were mostly modest in size, variable in design and short-term. The author concluded screening is reasonable for workers aged 50 or older with 5 or more years of asbestos exposure beginning 20 or more years earlier, plus either at least 10 pack-years of smoking (no limit on years since quitting) or other lung cancer risk factors. Workers with shorter but especially intense exposure should also be considered. Whether to screen never smokers without other risk factors was uncertain.

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: Narrative review by a single author, with a database literature search; not a full systematic review or meta-analysis
• Who was studied: Published studies found in MEDLINE, EMBASE and Web of Science up to 31 December 2021. Of 16 studies identified, nine non-randomized studies of asbestos-exposed populations with at least 150 participants, published 2002 to 2019, were included. The review also discussed other screening trials and risk models.
• Exposure: Asbestos exposure, defined differently across the studies (by industry, occupation, duration of employment, presence or absence of pleural plaques). Half of the studies required 15 or more years of exposure and half required 1 or 5 years. Fiber types were not generally specified, except one study of mostly environmental Libby amphibole exposure.
• Main results:
  • Across the nine studies combined, 86 lung cancers were detected among 5548 ever smokers (1.55%) and 6 among 1787 never smokers (0.33%).
  • Studies with the highest lung cancer detection yields tended to have the highest prevalence of pleural plaques (43% to 89%).
  • Only one study (Barbone and colleagues, Northeastern Italy) reported lung cancer mortality follow-up. It compared 926 asbestos-exposed workers screened by low-dose CT with 1507 people screened by chest X-ray. Compared with regional mortality rates, the lung cancer SMR was 0.55 (95% CI: 0.24 to 1.09) in the CT group and 2.07 (95% CI: 1.53 to 2.71) in the X-ray group.
  • In the same Italian study, after adjusting for age, smoking and asbestos exposure level, the CT group's lung cancer hazard ratio was 0.41 (95% CI: 0.17 to 0.96) versus the X-ray group.
• The authors' conclusion: The author concluded that it is reasonable to offer low-dose CT lung cancer screening to workers aged 50 or older with 5 or more years of asbestos exposure, beginning 20 or more years previously, who have smoked at least 10 pack-years (with no limit on years since quitting for former smokers), or who have other lung cancer risk factors. Workers with less than 5 years of especially intense exposure should also be considered. The author considered it uncertain whether screening is justified for never smokers with no other risk factors. The author called promoting screening an urgent priority.
• Limitations the authors state:
  • There have been no randomized clinical trials of low-dose CT screening among asbestos-exposed populations.
  • The studies in asbestos-exposed populations were mostly modest in size, variable in design, and short in follow-up.
  • Comparison of the combined yields with the large NLST and NELSON trials was not possible because the study populations differed and lacked detail on smoking and age.
  • In the Italian mortality study, differences in risk factors between groups and the non-random design likely explained some of the difference in lung cancer deaths.
  • Risk prediction models that include asbestos have not included enough asbestos-exposed people to give useful conclusions.

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, Asbestos Exposure, Lung Cancer, Clinical Trial, Fibrosis.

Related studies

• Lung cancer screening an asbestos exposed population: Existing lung cancer risk criteria are not sufficient — F.J.H. Brims, E.J.A. Harris, et al. (2023)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• Modelling prevalence and incidence of fibrosis and pleural plaques in asbestos-exposed populations for screening and follow-up: a cross-sectional study — C. Paris, A. Martin, et al. (2008)
• Low-dose computed tomography screening for lung cancer and pleural mesothelioma in an asbestos-exposed population: baseline results of a prospective, nonrandomized feasibility trial--an Alpe-adria Thoracic Oncology Multidisciplinary Group Study (ATOM 002) — G. Fasola, O. Belvedere, 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)
• Imaging of malignant pleural mesothelioma: it is possible a screening or early diagnosis program?-a systematic review about the use of screening programs in a population of asbestos exposed workers — F. Falaschi, C. Romei, et al. (2018)

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