Absence of radiographic asbestosis and the risk of lung cancer among asbestos-cement workers: Extended follow-up of a cohort

Our plain-English summary of Absence of radiographic asbestosis and the risk of lung cancer among asbestos-cement workers: Extended follow-up of a cohort, by M.M. Finkelstein (American Journal of Industrial Medicine, 2010).

The study

• Author: M.M. Finkelstein
• Journal: American Journal of Industrial Medicine
• Published: 2010;53(11):1065-9
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: It has been a matter of controversy whether there is an increased risk of lung cancer among asbestos-exposed workers without radiographic asbestosis. A previous study of lung cancer risk among asbestos-cement workers has been updated with an additional 12 years of follow-up.

Methods: Subjects had received radiographic examination at 20 and 25 years from first exposure to asbestos. Radiographs were interpreted by a single National Institute of Safety and Health (NIOSH)-certified B-reader using the 1971 International Labor Office (ILO) Classification of the pneumoconioses as reference standard. Asbestosis was defined as an ILO coding of 1/0 or higher. Standardized Mortality Ratios (SMRs) were calculated using the general population of Ontario as reference.

Results: Among asbestos-cement workers without radiographic asbestosis at 20 years latency the lung cancer SMR was 3.84 (2.24-6.14). Among workers without asbestosis when examined at 25 years latency the SMR was 3.69 (1.59-7.26).

Conclusions: Workers from an Ontario asbestos-cement factory who did not have radiographic asbestosis at 20 or 25 years from first exposure to asbestos continued to have an increased risk of death from lung cancer during an additional 12 years of follow-up.

© 2010 Wiley-Liss, Inc.

In plain English

This study extended the follow-up of asbestos-cement workers the same author had studied before. The men worked at the Johns-Manville asbestos cement plant in Scarborough, Ontario. Of 186 eligible men, 156 had X-rays available. Their deaths up to 1997 were compared with those of Ontario men. Among the 140 men without asbestosis on X-ray 20 years after first exposure, the lung cancer standardized mortality ratio (SMR) for the whole follow-up was 3.84 (2.24 to 6.14). Among the 117 men without asbestosis at 25 years, it was 3.69 (1.59 to 7.26). For 1986 to 1997 alone, the SMRs in these two groups were 2.18 (0.71 to 5.10) and 3.60 (0.98 to 9.23). Fewer than 25% of the men without asbestosis had never smoked. The author concluded that men without radiographic asbestosis continued to be at substantially increased risk of lung cancer. The author noted that 30 men were excluded and that X-rays may have been under-read. The author judged substantial under-reading unlikely, and judged it unlikely that lung cancer risk differed substantially between men without asbestosis who were included and those lost to follow-up.

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 mortality study (extended follow-up of an earlier study), comparing deaths with Ontario male population rates using standardized mortality ratios
• Who was studied: Men employed at the Johns-Manville asbestos cement plant in Scarborough, Ontario. 186 were eligible and 156 had at least one X-ray available. Mortality was followed to the end of 1997.
• Exposure: Production work at an asbestos-cement plant (hired before 1960, employed 9 years or more, at least 12 months in asbestos exposure). The article does not name the fiber types.
• Main results:
  • Men without radiographic asbestosis at 20 years from first exposure: lung cancer SMR 5.60 (2.90–9.80) during 1968–1985
  • Same group, 1986–1997: lung cancer SMR 2.18 (0.71–5.10). The difference between the two periods was not statistically significant (P = 0.08).
  • Men without radiographic asbestosis at 20 years (140 men): lung cancer SMR for the entire follow-up 3.84 (2.24–6.14)
  • Men without radiographic asbestosis at 25 years (117 men): lung cancer SMR 3.76 (1.03–9.66) in 1968–1985 and 3.60 (0.98–9.23) in 1986–1997. The difference was not statistically significant (P = 0.95).
  • Men without radiographic asbestosis at 25 years: lung cancer SMR for the entire follow-up 3.69 (1.59–7.26)
  • Fewer than 25% of men without radiographic asbestosis had never smoked. A Canadian survey reported 32% of men aged 35–54 and 26% of men 55 and over as never smokers. The author judged that smoking alone was unlikely to account for the elevated lung cancer SMRs.
  • Eight deaths were reported as pleural (3) or peritoneal (5) mesothelioma. Only one of these men had been recorded as having radiographic asbestosis.
  • The author found and corrected an error in the 1997 analysis concerning the date of entry to follow-up. The author described the changes to the earlier SMRs as small.
• The authors' conclusion: The author concluded that men without radiographic asbestosis (ILO code below 1/0) continued to be at substantially increased risk of lung cancer during the extra 12 years of follow-up.
• Limitations the authors state:
  • 30 of 186 eligible men (16%) were excluded because X-rays were not available.
  • The author judged it unlikely that lung cancer risk differed substantially between men without asbestosis who were included in the cohort and those lost to follow-up.
  • Because of how surveillance worked, men with abnormal X-rays were more likely to be included in follow-up.
  • A single reader interpreted all X-rays. Under-reading would overestimate lung cancer risk in men with normal X-rays. The author considered substantial under-reading unlikely, because this reader's interpretations had correlated well with pathology.
  • Follow-up could not be extended beyond 1997 because of funding limitations.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Asbestos-Cement, NIOSH, B-Reader, standardized mortality ratio (SMR), Latency.

Related studies

• Regarding "absence of radiographic asbestosis and the risk of lung cancer among asbestos-cement workers: extended follow-up of a cohort", by Murray Finkelstein, American Journal of Industrial Medicine 2010 — R.M. Ross (2011)
• Radiographic asbestosis is not a prerequisite for asbestos-associated lung cancer in Ontario asbestos-cement workers — M.M. Finkelstein (1997)
• Extended Mortality Follow-up of a Cohort of 25,460 Workers Exposed to Acrylonitrile — S. Koutros, J.H. Lubin, et al. (2019)
• Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers — C. Magnani, D. Ferrante, et al. (2008)
• Lung function predicts survival in a cohort of asbestos cement workers — H. Moshammer, M. Neuberger (2009)
• Radiographic abnormalities among asbestos-cement workers. An exposure-response study — M.M. Finkelstein, J.J. Vingilis (1984)

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