A critique to a review on the relationship between asbestos exposure and the risk of mesothelioma

Our plain-English summary of A critique to a review on the relationship between asbestos exposure and the risk of mesothelioma, by B. Terracini, D. Mirabelli, C. Magnani, et al (European Journal of Cancer Prevention, 2014).

The study

• Authors: B. Terracini, D. Mirabelli, C. Magnani, D. Ferrante, F. Barone-Adesi, M. Bertolotti
• Journal: European Journal of Cancer Prevention
• Published: 2014;23(5):492-4
• Type of article: Letter, Comment
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

This letter to the editor responded to a 2012 review by La Vecchia and Boffetta, which concluded that the risk of mesothelioma is not influenced by later exposure to asbestos or by stopping exposure. The authors said the review was not systematic and misread their own cohort study of Eternit asbestos-cement workers in Casale Monferrato, Italy. In that study, the category of workers who stopped exposure less than 3 years before death also included person-years accrued during employment, which made its risk appear artificially low. The other categories suggested a decreasing trend with longer time since exposure ended. The review also omitted the steady increase in rate ratio with duration of exposure: each year of exposure was associated with a 5% increase in mesothelioma risk. The authors argued that the SIA textile cohort estimates were unstable (for example, an SMR of 54.3 based on five cases) and confounded by exposure intensity. They described results from a UK case-control study as contradictory. They said the Great Britain Asbestos Survey gave no valid information beyond 30 years after exposure ended (one case). They concluded that the review's conclusions were not supported by the original studies. Several authors declared that they had acted as expert witnesses in asbestos criminal trials.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This letter to the editor was written by the authors of an earlier study of workers at the Eternit asbestos-cement plant in Casale Monferrato, Italy. It disputed a 2012 review by La Vecchia and Boffetta, which had concluded that later exposure does not appreciably change mesothelioma risk for workers first exposed long ago. The letter was not a new study. The authors reproduced a table from their 2008 study of deaths from pleural cancer. They argued that the review misread it. The group that had stopped exposure less than 3 years earlier (rate ratio 0.67, 95% confidence interval 0.32–1.40) also included time while workers were still employed, which made its risk look artificially low. The authors pointed to a suggested decline in risk with longer time since exposure ended. They also cited their finding that each year of exposure was associated with a 5% increase in mesothelioma risk. They argued that other studies in the review gave unstable estimates or uninformative analyses, and that pleural and peritoneal mesothelioma behave differently. The authors concluded that the review's view on recent exposures was not supported by their findings.

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: Letter to the editor critiquing a published review (La Vecchia and Boffetta, 2012). It re-presents results from the letter writers' own earlier cohort study (Magnani et al., 2008) and comments on other studies cited in the review. It reports no new data.
• Who was studied: The letter discusses the cohort of workers at the Eternit asbestos-cement plant in Casale Monferrato, Italy, from the authors' 2008 study. Cohort size and study dates are not given in this letter. It also comments on the SIA cohort, a UK case-control study (Rake et al., 2009) and the Great Britain Asbestos Survey.
• Exposure: Occupational asbestos exposure in asbestos-cement work, analysed by duration of exposure, time since first exposure (latency) and time since exposure ended. Fiber types are not named in the letter.
• Main results:
  • In the reproduced Eternit table (pleural malignant neoplasms), the rate ratio for workers whose exposure had ended less than 3 years earlier was 0.67 (95% CI 0.32–1.40, 13 cases), compared with 3–15 years (reference). For more than 30 years it was 0.65 (95% CI 0.26–1.63, 16 cases). The authors said the less-than-3-years group also included person-years accrued during employment, which made its risk appear artificially lower.
  • The authors described a suggested, not a definite, decreasing trend in rate ratio with longer time since exposure ended in the three categories other than less than 3 years. For 15–30 years the rate ratio was 0.90 (95% CI 0.54–1.49).
  • In the Eternit cohort, risk rose with duration of exposure after adjustment for latency and time since exposure ended. Compared with 10–19 years (reference), the rate ratio was 1.46 (95% CI 0.86–2.45) for 20–29 years and 1.88 (95% CI 0.93–3.83) for 30 or more years.
  • With duration fitted as a continuous variable, each year of exposure was associated with a 5% increase in the risk of mesothelioma in the Eternit study.
  • For the SIA cohort, the authors said the relevant estimates were unstable. The SMR of 54.3 (95% CI 18.0–130.1), for workers hired before age 30 and exposed for more than 10 years after age 30, rested on five cases and 2519 person-years. The comparison SMR was 80.8 (95% CI 40.0–153.4) for those exposed less than 10 years. The authors added that no adjustment was made for exposure intensity, so the results were confounded by intensity.
  • For the Great Britain Asbestos Survey, the authors said the period more than 30 years after exposure ended gave no valid information: one case, with a 95% CI for the RR of 0.14 to 7.02. That study also did not distinguish pleural from peritoneal mesothelioma.
  • For the UK case-control study (Rake et al., 2009), the authors described the results as contradictory. They said some findings may support, rather than contradict, the view that continuing exposure increases risk.
  • The authors criticized the review for not considering that pleural and peritoneal mesotheliomas relate differently to time-related variables.
• The authors' conclusion: The authors concluded that La Vecchia and Boffetta's view on recent exposures to asbestos was not supported by the Eternit findings. They also disagreed with the review's overall conclusion that, for workers exposed in the distant past, mesothelioma risk is not appreciably influenced by later exposures.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Mesothelioma, Cohort Study, Eternit, Asbestos-Cement, Casale Monferrato, rate ratio, Case-Control Study.

Related studies

• A critique of a review on the relationship between asbestos exposure and the risk of mesothelioma: reply — C. La Vecchia, P. Boffetta (2014)
• Pleural mesothelioma and occupational and non-occupational asbestos exposure: a case-control study with quantitative risk assessment — D. Ferrante, D. Mirabelli, et al. (2016)
• Pooled analysis of NAT2 genotypes as risk factors for asbestos-related malignant mesothelioma — M. Betti, M. Neri, et al. (2009)
• Increased risk of malignant mesothelioma of the pleura after residential or domestic exposure to asbestos: a case-control study in Casale Monferrato, Italy — C. Magnani, P. Dalmasso, et al. (2001)
• Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers — C. Magnani, D. Ferrante, et al. (2008)
• A review and critique of U.S. EPA's risk assessments for asbestos — S.H. Moolgavkar, E.L. Anderson, et al. (2014)

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