Occupational exposures and cancer of the larynx-systematic review and meta-analysis

Our plain-English summary of Occupational exposures and cancer of the larynx-systematic review and meta-analysis, by S. Paget-Bailly, D. Cyr, D. Luce (Journal of Occupational and Environmental Medicine, 2012).

The study

• Authors: S. Paget-Bailly, D. Cyr, D. Luce
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2012;54(1):71-84
• Type of article: Meta-analysis, Systematic review
• Cited by: 64 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To review epidemiologic data on occupational exposures and laryngeal cancer.

Methods: We performed a systematic literature search and a series of meta-analyses for agents with at least 10 available studies with homogenous exposure.

Results: We analyzed 99 publications. Significantly increased meta-relative risks (meta-RRs) were obtained considering exposure to polycyclic aromatic hydrocarbons (meta-RR 1.29; 95% confidence interval [CI] 1.10 to 1.52), engine exhaust (meta-RR 1.17; 95% CI 1.05 to 1.30), textile dust (meta-RR 1.41; 95% CI 1.09 to 1.83), and working in the rubber industry (meta-RR 1.39; 95% CI 1.13 to 1.71). Exposures to wood dust, formaldehyde, and cement dust were not significantly associated with laryngeal cancer. In regards of the epidemiologic available data, we could not conclude on the role of solvents.

Conclusion: Further studies should overcome past limitations in terms of exposure characterization, adjustment for confounding, and sample size.

In plain English

This systematic review and meta-analysis covered 99 publications on job exposures and laryngeal (voice box) cancer, in French or English from 1980 to 2010. They pooled agents with ten or more studies of homogeneous exposure. The authors called asbestos an already admitted risk factor and did not pool asbestos studies; one rubber-worker cohort gave asbestos hazard rate ratios of 2.3 (95% CI 0.5 to 10.2, medium exposure) and 4.7 (95% CI 0.5 to 42.8, high exposure). Pooled relative risks were raised for polycyclic aromatic hydrocarbons (1.29; 95% CI 1.10 to 1.52), engine exhaust (1.17; 95% CI 1.05 to 1.30), textile dust (1.41; 95% CI 1.09 to 1.83) and rubber industry work (1.39; 95% CI 1.13 to 1.71). Wood dust, formaldehyde and cement dust results were not statistically significant. Solvents were not pooled: fewer than ten studies covered "all solvents", and trichloroethylene and perchloroethylene reviews existed. The authors concluded this was some evidence of association for these four, but drew no firm overall conclusions. They noted small studies and missing smoking and alcohol data in most cohorts.

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 literature review with a series of random-effects meta-analyses, done for agents with at least 10 available studies with homogenous exposure
• Who was studied: 99 publications identified through PubMed and reference lists, published in French or English between 1980 and 2010. Of these, 30 came from case-control studies, 65 from cohort studies and four from record-linkage studies.
• Exposure: Occupational exposures not yet established as risk factors: polycyclic aromatic hydrocarbons, engine exhaust (diesel and gasoline), wood dust, textile dust, rubber industry work, formaldehyde, cement dust, solvents, metal working fluids and man-made vitreous fibers. The authors named asbestos as an already admitted risk factor and stated that established risk factors would not be detailed. They did not pool asbestos studies, but they reported asbestos results from one rubber-worker cohort.
• Main results:
  • Polycyclic aromatic hydrocarbons, 29 studies: meta-RR 1.29 (95% CI 1.10 to 1.52) using the high-exposure result, and 1.25 (95% CI 1.05 to 1.48) using the low-exposure result
  • Engine exhaust, 16 studies: overall meta-RR 1.17 (95% CI 1.05 to 1.30) using the high-exposure result, and 1.18 (95% CI 1.06 to 1.32) using the low-exposure result
  • Textile dust, 14 studies: overall meta-RRs 1.41 (95% CI 1.09 to 1.83) and 1.30 (95% CI 1.01 to 1.67), using the high and low cumulative exposure results respectively. The authors noted that publication bias was possible.
  • Working in the rubber industry, 14 studies: meta-RR 1.39 (95% CI 1.13 to 1.71)
  • Asbestos, from one cohort of rubber workers that the review reported (Straif et al), not from a pooled analysis: hazard rate ratios of 2.3 (95% CI 0.5 to 10.2) for the medium asbestos exposure category and 4.7 (95% CI 0.5 to 42.8) for the high exposure category
  • Wood dust, 22 studies: meta-RR 0.95 (95% CI 0.80 to 1.14) using high-exposure results, unchanged at 0.95 (95% CI 0.81 to 1.12) using low-exposure results
  • Formaldehyde, 11 studies: meta-RR 1.13 (95% CI 0.98 to 1.31), not statistically significant
  • Cement dust, 12 studies: meta-RR 1.11 (95% CI 0.90 to 1.38), slightly but not statistically significantly increased
  • Solvents: no meta-analysis was performed. Fewer than 10 studies were available for the exposure category "all solvents", and a meta-analysis on trichloroethylene and a review on perchloroethylene had already been published.
• The authors' conclusion: The authors concluded that their results provide some evidence of an association between laryngeal cancer and PAHs, engine exhaust, the textile industry and the rubber industry. They concluded that the data did not support an association with wood dust, cement dust or formaldehyde. Overall they could not draw firm conclusions, and they called for further study.
• Limitations the authors state:
  • Small sample sizes in most studies limited the statistical power to detect moderate increases in risk
  • Most cohort studies lacked data on confounders such as alcohol and tobacco use
  • Detailed exposure assessment was often missing, so dose-response patterns could not be evaluated
  • Restricting the review to studies published from 1980 onward could have led to a loss of information
  • Reporting bias was possible, because many occupational cohort studies did not report results for laryngeal cancer

Topics

The National Library of Medicine indexes this study under subjects our site covers: Throat and laryngeal cancer.

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

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