Occupational exposure to asbestos and risk of kidney cancer: an updated meta-analysis

Our plain-English summary of Occupational exposure to asbestos and risk of kidney cancer: an updated meta-analysis, by C. Zunarelli, A. Godono, G. Visci, et al (European Journal of Epidemiology, 2021).

The study

• Authors: C. Zunarelli, A. Godono, G. Visci, F.S. Violante, P. Boffetta
• Journal: European Journal of Epidemiology
• Published: 2021;36(9):927-936
• Type of article: Meta-analysis, Systematic review
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Limited information is available on carcinogenicity of asbestos on non-respiratory organs. We aimed at conducted an updated systematic review and meta-analysis of cohort studies on occupational exposure to asbestos and risk of kidney cancer. We searched through three databases, PubMed, Embase and Scopus for article published after 2000, and after eliminating duplicates and non-relevant studies, we identified 13 studies. We combined their results with those of 31 non-overlapping studies included in a previous review up to 2000. We conducted a meta-analysis based on random-effects models. The pooled relative risk of kidney cancer for asbestos exposure was 0.94 (95% confidence interval, 0.84-1.04), with no differences according to type of asbestos fiber, geographic region, period of exposure, or estimated quality of the study. Our results showed a lack of association between occupational asbestos exposure and risk of kidney cancer.

© 2021. The Author(s).

In plain English

This was an updated systematic review and meta-analysis, a statistical pooling of earlier cohort studies, of kidney cancer risk in workers occupationally exposed to asbestos. The authors searched three databases for 2001 to May 2020 and reused 29 of 33 studies from a 2000 meta-analysis. They ended with 42 studies giving 54 results from 51 cohorts. The results section gave a pooled relative risk of 1.14 (95% CI 1.04–1.29). It was 0.98 (0.79–1.22) for incidence studies and 1.15 (0.99–1.34) for mortality studies. The discussion rounds this to 1.1 (1.0–1.3), but the abstract gives 0.94 (0.84–1.04) without explanation. The authors wrote that results did not differ by fiber type, region, sex or period of first exposure. Their table shows 1.45 (1.14–1.85) for North American cohorts, with a heterogeneity p-value of 0.13 across regions. For workers first employed 1945–1960 it shows 1.47 (1.09–1.99), with a heterogeneity p-value of 0.001 across periods. The authors concluded that their results showed a lack of association. They noted that only three studies considered smoking as a potential confounder.

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 and meta-analysis of cohort and nested case-control studies, using random-effects models, updating a meta-analysis of studies published up to 2000
• Who was studied: 42 studies in total. Thirteen came from a search of PubMed, Scopus and Embase covering 2001 to May 2020. The other 29 were non-overlapping studies out of 33 in the earlier meta-analysis; four were left out because newer studies had updated their data. Together the 42 studies gave 54 results from 51 cohorts. Of the cohorts, 34 were predominantly men, six predominantly women and 11 both. By region, 34 were from Europe, nine from North America and eight from other countries.
• Exposure: Workers with exclusive or predominant occupational exposure to asbestos, including asbestos cement, textile, shipyard, insulation, mining and milling, and product manufacture. The main fiber was chrysotile in 21 cohorts and amphiboles in seven; in 23 cohorts the fiber type could not be distinguished.
• Main results:
  • Pooled relative risk of kidney cancer across all included results, as printed in the results section: 1.14 (95% CI 1.04–1.29). Results based on zero observed events were excluded.
  • The discussion gives a rounded version of the pooled result: relative risk 1.1 (95% CI 1.0–1.3)
  • Limited evidence of differences between study results (heterogeneity p = 0.3; I2 = 11%)
  • Studies of cancer incidence: summary relative risk 0.98 (95% CI 0.79–1.22)
  • Studies of mortality: summary relative risk 1.15 (95% CI 0.99–1.34)
  • The authors reported no difference in stratified analyses by asbestos type, region, sex, or period of first exposure
  • In Table 2, the pooled relative risk for North American cohorts (9 risk estimates) was 1.45 (95% CI 1.14–1.85). The heterogeneity p-value across geographic regions was 0.13.
  • In Table 2, the pooled relative risk for cohorts first employed 1945–1960 (9 risk estimates) was 1.47 (95% CI 1.09–1.99). The heterogeneity p-value across periods of first employment was 0.001.
  • No evidence of publication bias: Egger's test p-value 0.4 for mortality studies and 0.9 for incidence studies
  • Of the studies published after 2000, only two were rated good quality and eight moderate quality
• The authors' conclusion: The authors concluded that their results showed a lack of association between occupational asbestos exposure and risk of kidney cancer
• Limitations the authors state:
  • Studies with no kidney cancer cases could not be included in the main analysis, which used log-transformed measures. An analysis without log transformation did not materially change the results.
  • Few studies were based on cancer incidence. Mortality studies may be affected by survival factors such as access to treatment.
  • Cause of death on death certificates may be inaccurate, especially in elderly people
  • Only three studies considered smoking as a potential confounding factor. None included obesity, alcohol, diabetes, hypertension or analgesic therapy.
  • Only two studies reported latency or duration of exposure, so no dose-response analysis was done
  • Exposure was often assessed by job title or industry without direct measurements, which does not distinguish different exposure levels and may underestimate effects

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Meta-Analysis, Systematic Review, Relative Risk, Asbestos Exposure, confidence interval.

Related studies

• Kidney cancer and occupational exposure to asbestos: a meta-analysis of occupational cohort studies — D. Sali, P. Boffetta (2000)
• Occupational Asbestos Exposure and Kidney Cancer: Systematic Review and Meta-analysis of Cohort Studies — C.C.Y. Pang, K. Phan, et al. (2021)
• Heavy metals, welding fumes, and other occupational exposures, and the risk of kidney cancer: A population-based nested case-control study in three Nordic countries — I.M. Michalek, J.I. Martinsen, et al. (2019)
• Occupational exposure to dusts and risk of renal cell carcinoma — S. Karami, P. Boffetta, et al. (2011)
• Workplace exposure to asbestos and the risk of kidney cancer in Canadian men — C.E. Peters, M.É. Parent, et al. (2018)
• Occupational risk factors for renal cell cancer: a case--control study in northern Italy — S. Mattioli, D. Truffelli, et al. (2002)

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