Re: Dutheil et al. Prostate Cancer and Asbestos: A Systematic Review and Meta-Analysis

Our plain-English summary of Re: Dutheil et al. Prostate Cancer and Asbestos: A Systematic Review and Meta-Analysis, by P. Boffetta, N. Franco, A. Gullino, et al (The Permanente Journal, 2021).

The study

• Authors: P. Boffetta, N. Franco, A. Gullino, E. Pira
• Journal: The Permanente Journal
• Published: 2021;25
• Type of article: Letter, Comment
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

In plain English

This is a letter to the editor, not a new study. The authors criticized a published systematic review and meta-analysis by Dutheil and colleagues on asbestos and prostate cancer, saying it had several methodological errors. Using a quick, non-systematic search, they listed 10 studies of asbestos-exposed workers with prostate cancer results that the review had not included; for 4 of these, the review had used earlier, outdated reports of the same cohorts. These included the two largest, Lin et al. 2015 (Taiwan) and Ferrante et al. 2017 (Italy). In their table, Lin et al. reported a standardized incidence ratio of 0.67 (95% CI 0.59-0.75) based on 307 cases. Ferrante et al. reported a standardized mortality ratio of 0.97 (0.87-1.08) based on 352 deaths. The authors also said the review counted one Australian crocidolite cohort twice, and they questioned the inclusion of an oil refinery cohort. They argued that combining incidence and mortality data was a mistake. The authors concluded that the meta-analysis results were not interpretable and that its conclusion linking asbestos exposure to prostate cancer was not justified. A reply from the review's authors, printed alongside, is not summarized here.

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 criticizing a published systematic review and meta-analysis; it includes a table of studies the letter's authors found through a quick, non-systematic literature search
• Who was studied: 10 published cohort studies of asbestos-exposed workers (insulation product manufacture, insulation workers, shipyard, cement, textile, mining and mixed industries) in the UK, US, Canada, Sweden, Norway, Taiwan and Italy, ranging from 541 to 121883 workers, that had not been included in the Dutheil et al. review
• Exposure: Occupational asbestos exposure; the fiber types listed in the table were amosite, chrysotile, predominantly chrysotile, and mixed fibers (one study not available)
• Main results:
  • The authors identified 10 studies with prostate cancer results among asbestos-exposed workers that the review did not include. For 4 of these, the review had included outdated results.
  • For the cohorts marked in the table, an earlier report of the same cohort had been included in the Dutheil et al. review
  • The table gives an SMR for each study. SMR means standardized mortality ratio, or standardized incidence ratio for studies on prostate cancer incidence.
  • The authors said the two studies with the largest number of prostate cancer cases or deaths were not in the meta-analysis.
  • Lin et al. 2015: mixed industry and mixed fibers, Taiwan, prostate cancer incidence, 121883 male workers, 307 observed cases, ratio 0.67 (95% CI 0.59-0.75)
  • Ferrante et al. 2017: mixed industry and mixed fibers, Italy, prostate cancer mortality, 46060 male workers, 352 observed deaths, SMR 0.97 (95% CI 0.87-1.08)
  • Selikoff and Seidman 1991: insulation workers, mixed fibers, US and Canada, mortality, 17800 men, 59 deaths, SMR 1.12 (95% CI 0.85-1.45)
  • Pira et al. 2017: chrysotile miners in Italy, workers at high asbestos exposure, mortality, 1056 men, 9 deaths, SMR 0.91 (95% CI 0.42-1.74)
  • The authors argued that the review double-counted observations, because two included papers referred to the same cohort of Australian crocidolite workers
  • The authors questioned including an oil refinery worker cohort, because these workers are exposed to other potential carcinogens
  • The authors argued it was a mistake to combine prostate cancer incidence and mortality results. In their view, incidence is sensitive to screening with prostate specific antigen, while mortality depends on access to effective treatment.
• The authors' conclusion: The authors concluded that the results of the Dutheil et al. meta-analysis were not interpretable and that its conclusion that asbestos exposure is associated with prostate cancer was not justified
• Limitations the authors state:
  • The authors stated that their own search for missing studies was quick and not systematic

Topics

Medical terms in this study, explained in our Lexicon: Systematic Review, Meta-Analysis.

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