Lung cancer risk and occupational pulmonary fibrosis: systematic review and meta-analysis

Our plain-English summary of Lung cancer risk and occupational pulmonary fibrosis: systematic review and meta-analysis, by J. Krabbe, K.M. Steffens, S. Drießen, et al (European Respiratory Review, 2024).

The study

• Authors: J. Krabbe, K.M. Steffens, S. Drießen, T. Kraus
• Journal: European Respiratory Review
• Published: 2024;33(171)
• Type of article: Meta-analysis, Systematic review
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Molecular pathways found to be important in pulmonary fibrosis are also involved in cancer pathogenesis, suggesting common pathways in the development of pulmonary fibrosis and lung cancer.

Research Question: Is pulmonary fibrosis from exposure to occupational carcinogens an independent risk factor for lung cancer?

Study Design And Methods: A comprehensive search of PubMed, Embase, Web of Science and Cochrane databases with over 100 search terms regarding occupational hazards causing pulmonary fibrosis was conducted. After screening and extraction, quality of evidence and eligibility criteria for meta-analysis were assessed. Meta-analysis was performed using a random-effects model.

Results: 52 studies were identified for systematic review. Meta-analysis of subgroups identified silicosis as a risk factor for lung cancer when investigating odds ratios for silicosis in autopsy studies (OR 1.47, 95% CI 1.13-1.90) and for lung cancer mortality in patients with silicosis (OR 3.21, 95% CI 2.67-3.87). Only considering studies with an adjustment for smoking as a confounder identified a significant increase in lung cancer risk (OR 1.58, 95% CI 1.34-1.87). However, due to a lack of studies including cumulative exposure, no adjustments could be included. In a qualitative review, no definitive conclusion could be reached for asbestosis and silicosis as independent risk factors for lung cancer, partly because the studies did not take cumulative exposure into account.

Interpretation: This systematic review confirms the current knowledge regarding asbestosis and silicosis, indicating a higher risk of lung cancer in exposed individuals compared to exposed workers without fibrosis. These individuals should be monitored for lung cancer, especially when asbestosis or silicosis is present.

Copyright ©The authors 2024.

In plain English

This was a systematic review and meta-analysis asking whether lung scarring (pulmonary fibrosis) caused by workplace exposures is a risk factor for lung cancer. The authors searched four databases for studies published through May 2021 that compared exposed adults with and without fibrosis. They included 52 studies: 21 on asbestos, 25 on silica and six on mixed and coal dusts. The asbestos studies differed too much to be pooled. In their written review, the authors judged that asbestosis could be a potential independent risk factor for lung cancer. For silica, pooled results showed higher odds of lung cancer in people with silicosis than without: OR 1.47 (95% CI 1.13–1.90) in studies of deceased patients, OR 3.21 (95% CI 2.67–3.87) for death from lung cancer, and OR 1.58 (95% CI 1.34–1.87) in eight smoking-adjusted studies. The authors said co-exposures and cumulative dose could not be excluded as explanations. Evidence on mixed and coal dusts was too weak for any statement. The authors concluded that asbestosis and silicosis indicate higher lung cancer risk, but that exposed people without fibrosis cannot be assumed free of risk.

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: Systematic review and meta-analysis (random-effects model) of observational studies
• Who was studied: 52 published studies of adults exposed to fibrosis-causing workplace hazards, comparing those with and without pulmonary fibrosis; searches covered articles through May 2021. There were 21 asbestos studies, 25 silica studies and 6 studies on other exposures (mixed and coal dusts).
• Exposure: Occupational exposures able to cause pulmonary fibrosis: asbestos (asbestosis), silica dust (silicosis), and mixed and coal dusts (pneumoconiosis); outcome was lung cancer
• Main results:
  • Asbestos: studies were too heterogeneous for a meta-analysis
  • Asbestos, narrative review: asbestosis identified as a potential independent risk factor for asbestos-related lung cancer (level of evidence rated moderate)
  • Silica, studies of deceased patients: higher lung cancer odds in people with silicosis than without, ORdead 1.47 (95% CI 1.13–1.90)
  • Silica, death from lung cancer: ORmortality 3.21 (95% CI 2.67–3.87) for people with silicosis
  • Silica, eight studies adjusted at least for smoking: OR 1.58 (95% CI 1.34–1.87) for people with silicosis compared with people without
  • Silica, narrative review: the authors could not exclude that the association depends on co-exposure and cumulative dose
  • Mining (mixed and coal dusts): very low level of evidence; no statement made
• The authors' conclusion: The authors concluded that the review confirms existing literature showing asbestosis and silicosis indicate a higher lung cancer risk in exposed individuals. They added that this does not show that exposed people without fibrosis have no lung cancer risk, or that asbestosis and silicosis are obligatory precursors of lung cancer.
• Limitations the authors state:
  • Only observational studies were included, so the highest confidence rating could not be reached
  • Included studies had small numbers of patients, few fibrosis cases, low statistical power or no adjustment for confounders
  • Most studies detected fibrosis by CT or radiographs, which may miss early or mild fibrosis
  • Heterogeneity prevented a meta-analysis for asbestosis and allowed only subgroup analyses for silicosis
  • Because few studies accounted for cumulative exposure, no definitive conclusion could be reached on whether asbestosis or silicosis are independent risk factors

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, Pulmonary Fibrosis, Systematic Review, Meta-Analysis, Silicosis, Odds Ratio, Autopsy, Cumulative Exposure.

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