Asbestos Exposure and Malignant Pleural Mesothelioma: A Systematic Review of Literature

Our plain-English summary of Asbestos Exposure and Malignant Pleural Mesothelioma: A Systematic Review of Literature, by C. Santos, M.D.A. Dixe, E. Sacadura-Leite, et al (Portuguese Journal of Public Health, 2023).

The study

• Authors: C. Santos, M.D.A. Dixe, E. Sacadura-Leite, P. Astoul, A. Sousa-Uva
• Journal: Portuguese Journal of Public Health
• Published: 2023;40(3):188-202
• Type of article: Review
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The relationship between exposure to asbestos and malignant pleural mesothelioma (MPM) is already well established. Nevertheless, much remains to be known about exposure thereto and the incidence and mortality from MPM.

Objective: This systematic review aims to map the relationship between asbestos and MPM by studying the exposure to asbestos and the incidence and mortality of MPM.

Methods: A systematic review was conducted relating asbestos and MPM. Exposure to asbestos, incidence, and mortality by MPM was reviewed. PubMed, Web of Science, Cochrane Library, RCAAP, DART-Europe, and the reference lists of included studies were searched, from January 1, 1960, to December 31, 2020. Methodological quality was checked, the risk of bias analysis was performed, a level of evidence grade was assigned, and descriptive data analysis was performed.

Results: 3,484 unique citations were identified, which included seventeen observational studies that met inclusion criteria with a total of 1,104 patients. Heterogeneity is present between the included studies which range from a case series of 16 retrospective studies and 1 prospective study. Studies were mostly conducted in Europe, particularly in Italy (6), and were published between 1969 and 2020. The mean age of patients is approximately 66 years with a latency period between the first exposure and diagnosis of approximately 42 years. 14 studies present data regarding the occupational context and chrysotile and crocidolite are the most studied types of fibre. The incidence of cases occurred between the interval 1966 and 2014 and in 9 studies the mortality rate was 100% of patients.

Conclusion: There is high evidence to support the relationships between asbestos and MPM. However, the relatively scant information provided by the studies reinforces the need for well-conducted research and implementation of National Mesothelioma Surveillance Centres at a global level.

Copyright © 2023 by The Author(s). Published by S. Karger AG, Basel on behalf of NOVA National School of Public Health.

In plain English

This article was a systematic review. The authors searched PubMed, Web of Science, the Cochrane Library and two grey-literature sources, covering January 1, 1960, to December 31, 2020, for studies on asbestos exposure and malignant pleural mesothelioma (MPM). Of 3,484 unique papers, 17 observational studies were included. They were published between 1969 and 2020 and covered 1,104 patients (855 male, 180 female, 69 unknown). The studies differed too much to be combined in a meta-analysis, so their results were described. Where reported, average age was about 66 years. Average latency from first exposure to diagnosis was about 42 years, ranging from 1 to 91 years. Only seven studies named the fiber type: chrysotile, crocidolite, amosite and anthophyllite. Shipbuilding, construction, making asbestos-containing products and mining were the main occupations. In twelve studies with data on deaths, more than 89% of patients had died, and 100% had died in nine of them. The authors concluded there is high evidence supporting the relationship between asbestos and MPM. They noted that many studies were of poor quality and at high risk of bias, and called for National Mesothelioma Surveillance Centres worldwide.

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: Systematic review of 17 observational studies (twelve analytical cross-sectional, three retrospective cohort, two retrospective case-control; sixteen retrospective and one prospective), reported following PRISMA 2020, with descriptive rather than meta-analytic synthesis
• Who was studied: 17 included studies with 1,104 MPM patients in total (855 male, 180 female, 69 unknown), published 1969 to 2020. Eleven studies were from Europe (six from Italy), one each from South Africa, the USA, Mexico and Australia, and two were joint Australia/UK and Australia/Italy studies. The literature search covered January 1, 1960, to December 31, 2020.
• Exposure: Asbestos exposure by inhalation. Seven studies concerned occupational exposure, two para-occupational (household) exposure, seven combined occupational and non-occupational (environmental and para-occupational) exposure, and one an unknown context. Fiber types reported in seven studies were chrysotile, crocidolite, amosite and anthophyllite.
• Main results:
  • Of 3,484 unique papers screened, 59 were read in full and 17 were included in the review.
  • In the twelve studies where it could be calculated, the average patient age was approximately 66 years, ranging from 30 to 93 years.
  • In twelve studies, the average latency period from first exposure to diagnosis was approximately 42 years, with a minimum of 1 year and a maximum of 91 years.
  • Only seven studies reported fiber type (chrysotile, crocidolite, amosite, anthophyllite). Chrysotile was identified in four studies and crocidolite in three.
  • Only one of the seventeen studies, an occupational study, presented cumulative exposure values.
  • In the fourteen studies concerning occupational exposure, the main occupations were shipbuilding, construction, production of asbestos-containing products, and mining.
  • In para-occupational (household) studies, women made up more than 83% of cases. In occupational studies, men made up between 67 and 100% of patients.
  • In the twelve studies with data on deaths by the time of publication, the mortality rate was more than 89%. In nine of those studies it was 100%.
  • In the four studies that reported it, the interval between diagnosis and death was approximately 1 year.
  • Heterogeneity in study design and outcomes prevented a meta-analysis, and results were reported descriptively.
• The authors' conclusion: The authors concluded there is high evidence to support the relationship between asbestos and MPM. They stated that many of the small number of identified studies were of poor methodological quality and at high risk of bias. They called for well-conducted research and for National Mesothelioma Surveillance Centres at a global level, which they described as mandatory.
• Limitations the authors state:
  • The included studies provided relatively scant information on asbestos exposure and on MPM incidence and mortality.
  • Heterogeneity of the studies prevented meta-analysis.
  • Only papers in English, French and Portuguese were considered, so relevant studies may have been missed.
  • Survival, diagnosis, treatment and compensation were not considered.
  • Because the search went back to 1960, many studies were not designed according to current quality guidelines.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pleural Mesothelioma, Systematic Review, Latency, Chrysotile, Crocidolite, Mesothelioma.

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