Prevalence of occupational exposure to asbestos and crystalline silica according to phenotypes of lung cancer from the CaProMat study: A case-only study

Our plain-English summary of Prevalence of occupational exposure to asbestos and crystalline silica according to phenotypes of lung cancer from the CaProMat study: A case-only study, by M. El Zoghbi, P. Salameh, I. Stücker, et al (American Journal of Industrial Medicine, 2018).

The study

• Authors: M. El Zoghbi, P. Salameh, I. Stücker, C. Paris, J.C. Pairon, A. Gislard, J. Siemiatycki, V. Bonneterre, B. Clin, P. Brochard, F. Delva, A. Lacourt
• Journal: American Journal of Industrial Medicine
• Published: 2018;61(1):85-99
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The objective of the study was to compare the prevalence of occupational exposure to asbestos and crystalline silica according to histological types of lung cancer and age at diagnosis.

Methods: CaProMat study is a pooled case-only study conducted between 1996 and 2011. The current study consisted of 6521 lung cancer cases. Occupational exposure to asbestos and crystalline silica was assessed by two Job-Exposure Matrices. A weighted prevalence of exposure was derived and compared according to histological types and age at diagnosis.

Results: There was no difference of weighted prevalence of exposure to asbestos and crystalline silica according to histological types of lung cancer. There was a statistically significant difference of weighted prevalence of exposure to asbestos and crystalline silica according to age at diagnosis.

Conclusions: Due to the limited clinical importance of the difference, neither the histological type, nor the age at diagnosis can be used as an indicator for the occupational exposure to asbestos or crystalline silica.

© 2017 Wiley Periodicals, Inc.

In plain English

This was a pooled case-only study of 6521 French men with lung cancer, recruited 1996 to 2011 from six French university hospitals and a population-based study. Using work histories and two job-exposure matrices, the authors estimated each man's probability of on-the-job exposure to asbestos and crystalline silica. They compared a 'weighted prevalence' of exposure across lung cancer types and ages at diagnosis. Overall, it was 33.9% (95% confidence interval 32.8 to 35.1) for asbestos and 25.7% (24.7 to 26.8) for crystalline silica. For asbestos, it did not differ significantly between lung cancer types (P = 0.13). For silica, the difference was borderline (P = 0.049), highest in squamous cell carcinoma. By age at diagnosis, differences were statistically significant for asbestos (P = 0.014) and silica (P = 0.018), lowest in men diagnosed at 70 or older. The authors considered all the differences weak and of limited clinical importance. They concluded that lung cancer type and age at diagnosis cannot be used as indicators of occupational asbestos or silica exposure. For the silica finding, they could not exclude residual confounding by smoking.

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: Pooled case-only study (lung cancer cases only, no comparison group without cancer), combining hospital-based and population-based case series
• Who was studied: 6521 French men with histologically confirmed lung cancer, recruited 1996 to 2011: 4400 hospital-based cases from six French university hospitals (RNV3P network) and 2121 population-based cases from the French ICARE study. Canadian cases in the wider CaProMat study were excluded.
• Exposure: Occupational exposure to asbestos (fiber types not analysed separately) and to crystalline silica. Exposure was assessed retrospectively from job histories (jobs held more than 6 months) using two job-exposure matrices that gave probability, frequency and intensity of exposure. From these, the authors derived a weighted prevalence and a cumulative exposure index.
• Main results:
  • Among all 6521 cases, 73.5% had held at least one job with a non-null probability of asbestos exposure, and 16.4% had a highest probability of exposure greater than 70%.
  • For crystalline silica, 39.0% of cases had held at least one job with a non-null probability of exposure, and 25.9% had a highest probability of exposure greater than 50%.
  • Overall weighted prevalence of exposure was 33.9% [95%CI: 32.8-35.1] for asbestos and 25.7% [95%CI: 24.7-26.8] for crystalline silica.
  • Asbestos weighted prevalence did not differ significantly between lung cancer types (P = 0.13). It ranged from 35.0% [95%CI: 33.0-37.1] in squamous cell carcinoma to 32.2% [95%CI: 28.8-35.5] in large cell carcinoma.
  • For crystalline silica, the difference between lung cancer types was borderline statistically significant (P = 0.049). It ranged from 27.7% [95%CI: 25.8-29.6] in squamous cell carcinoma to 23.5% [95%CI: 18.8-28.2] in other lung cancer types.
  • When stratified by smoking status, there were no significant differences between lung cancer types for asbestos. For silica, there was a borderline significant difference only among ex-smokers (P = 0.045).
  • By age at diagnosis, weighted prevalence differed significantly for asbestos (P = 0.014) and for crystalline silica (P = 0.018). The highest values were 35.5% [95%CI: 33.4-37.6] for asbestos in men diagnosed at 50-59 and 27.6% [95%CI: 24.3-30.9] for silica in men diagnosed under 50. The lowest values were in men diagnosed at 70 or older: 30.9% [95%CI: 28.7-33.1] for asbestos and 23.5% [95%CI: 21.5-25.5] for silica.
  • Among current smokers, asbestos weighted prevalence differed significantly by age at diagnosis (P = 0.003): 35.7% [95%CI: 31.8-39.6] in those diagnosed under 50 versus 29.2% [95%CI: 25.4-33.0] in those diagnosed at 70 or older. For silica, no significant age differences were found within smoking groups.
  • The authors judged that, although some differences were statistically significant, all were weak and of limited clinical importance.
• The authors' conclusion: The authors concluded that there was no major difference in occupational asbestos or crystalline silica exposure by lung cancer type or age at diagnosis. They stated that these features therefore cannot be used as indicators of occupational exposure, and that occupational exposure should be investigated whatever the histological type or age at diagnosis.
• Limitations the authors state:
  • For the higher silica exposure seen in squamous cell carcinoma, the authors could not exclude residual confounding by smoking.
  • The authors acknowledged that other publications have discussed the limitations of job-exposure matrices compared with other exposure assessment methods.
  • The study population, drawn largely from the general population, had a low fraction of substantially exposed workers.

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: Occupational Exposure, Crystalline, Lung Cancer.

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