Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': methodological problems with case-only survival analysis

Our plain-English summary of Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': methodological problems with case-only survival analysis, by D. Consonni, F. Barone-Adesi, C. Mensi (British Journal of Cancer, 2014).

The study

• Authors: D. Consonni, F. Barone-Adesi, C. Mensi
• Journal: British Journal of Cancer
• Published: 2014;111(8):1674
• Type of article: Letter, Comment
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Summary of the article

This letter commented on a 2013 article by Frost on mesothelioma latency in the GB Asbestos Survey, a prospective cohort of asbestos workers set up in 1971. Frost defined latency as the time from first occupational exposure to asbestos to death from mesothelioma, studied mesothelioma deaths in 1978–2005, and concluded that there was not sufficient evidence of an inverse relationship between exposure intensity and latency length. The letter's authors argued that the analysis was methodologically flawed. The cohort had 94 960 subjects, but only the 614 mesothelioma deaths were analysed. They explained that when follow-up ends before everyone has the outcome (censoring), the survival times of cases do not represent the whole cohort. They gave a fictitious trial of 40 subjects as an example. With complete follow-up, mean survival was 43 and 24 months and median survival was 33 and 15 months. When follow-up ended at 48 months, the means became 18 and 16 months and the medians 10 and 13 months, which made the groups look more similar than they were. They stated that a regression model would not solve this, and that more than 99% of mesothelioma survival times in Frost's study were not directly observable. They noted that the same problem had affected studies of mesothelioma registry case series. They concluded that Frost's results were not interpretable. They said latency should be analysed using all cohort members, treating those not dying of mesothelioma as censored.

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 is a letter to the editor, not an original study. The authors commented on a 2013 paper by Frost on mesothelioma latency (the time from first occupational asbestos exposure to death from mesothelioma) among British asbestos workers in the GB Asbestos Survey. According to the letter, Frost concluded there was not sufficient evidence that more intense asbestos exposure went with a shorter latency period. The authors argued that this analysis was flawed because only the 614 cohort members who died of mesothelioma were included, out of 94 960 workers. Using an invented example of a 40-person drug trial, they showed that when follow-up ends early, comparing average times only among those who died can make two groups look more similar than they really are. In that example, means of 43 and 24 months became 18 and 16 months. They wrote that more than 99% of mesothelioma survival times in Frost's study were not directly observable, and that the regression model used would not solve this. The authors concluded that Frost's results were not interpretable. They said all 94 960 workers should be analysed, with those who did not die of mesothelioma treated as 'censored'.

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 (methodological commentary) on a published cohort analysis, using a hypothetical numerical example; no new data
• Who was studied: No population of its own. The letter discusses Frost's (2013) analysis of the GB Asbestos Survey, a prospective cohort of 94 960 British asbestos workers established in 1971, in which 614 mesothelioma deaths from 1978 to 2005 were analysed. It also uses an invented example of 40 subjects (20 on a new drug, 20 on placebo).
• Exposure: Occupational asbestos exposure, with intensity of exposure examined in relation to latency in Frost's study. No fiber types are named in the letter.
• Main results:
  • The authors pointed out that Frost's analysis included only the 614 mesothelioma deaths, although the whole cohort of 94 960 subjects was available
  • In the authors' invented example with all 40 subjects followed until death, the experimental group and the placebo group had mean survival of 43 and 24 months and median survival of 33 and 15 months
  • In the same example, if the study ended at 48 months and only observed deaths were used, the means for the experimental and placebo groups became 18 and 16 months and the medians 10 and 13 months
  • The authors explained that stopping follow-up removes the longest survival times, making the groups' distributions look more similar than they are, and stated that this is a general phenomenon
  • The authors stated that in Frost's study more than 99% of mesothelioma survival times were not directly observable
  • The authors stated that the regression model used by Frost does not solve the problem
  • The authors stated that the same problem also affected earlier studies based on case series from mesothelioma registries
• The authors' conclusion: The authors concluded that Frost's results were not interpretable because they were based only on mesothelioma deaths. In their view, the only meaningful survival approach is to include all 94 960 workers and treat those not dying of mesothelioma as censored.

Topics

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

Medical terms in this study, explained in our Lexicon: Latency, Mesothelioma, Occupational Exposure, Median Overall Survival.

Related studies

• Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)' — D. Mirabelli, D. Zugna (2014)
• Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': the effect of left censoring — A. Farioli, S. Mattioli, et al. (2014)
• Response to comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)' — G. Frost (2014)
• The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005) — G. Frost (2013)
• Occupational exposures to cosmetic talc and risk of mesothelioma: an updated pooled cohort and statistical power analysis with consideration of latency period — G.M. Marsh, A.M. Ierardi, et al. (2019)
• Letter concerning: Occupational exposures to cosmetic talc and risk of mesothelioma: an updated pooled cohort and statistical power analysis with consideration of latency period by Gary M. Marsh et al. (Inhal Toxicol. 2019 Aug 5:1-11. doi:10.1080/08958378.2019.1645768) — M.M. Finkelstein (2019)

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