Oral and pharyngeal cancer risk associated with occupational carcinogenic substances: Systematic review

Our plain-English summary of Oral and pharyngeal cancer risk associated with occupational carcinogenic substances: Systematic review, by K.H. Awan, R. Hegde, V.J. Cheever, et al (Head & Neck, 2018).

The study

• Authors: K.H. Awan, R. Hegde, V.J. Cheever, W. Carroll, S. Khan, S. Patil, S. Warnakulasuriya
• Journal: Head & Neck
• Published: 2018;40(12):2724-2732
• Type of article: Systematic review
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Oral and pharyngeal cancers (OPC) represent the seventh most common type of cancer and the seventh leading cause of deaths by cancer worldwide. Few studies have assessed the occupational exposure risks associated with OPC and in many cases the results are conflicting. The aim of this study was to determine, through a systematic review, the association of OPC and exposure to different occupational carcinogenic substances.

Methods: The addressed focused question was "Is there an association of occupational carcinogenic substances with OPC?" PubMed, MEDLINE, EMBASE, and ISI Web of Science databases were searched between January 1995 up to and including July 2016 using the keywords "oral cancer," "pharyngeal cancer," "pharyngeal neoplasms," "oral neoplasms," "occupational disease," "occupational exposure," and "occupational risk factor" in various combinations. Letters to the Editor, review articles, case reports, and unpublished articles were excluded.

Results: Fourteen original articles were included. Majority of the studies were conducted in European countries and used a case-control design. The results showed a significant association between formaldehyde, wood dust, coal dust, asbestos, welding fumes, and risk of developing OPC, while marginal association was observed with metal and leather dust. No associated risk was observed for textile fibers.

Conclusion: There is some evidence to suggest associations of occupational substances with OPC, particularly in the pharynx. Future well-designed studies are required to confirm or rule out with confidence the associated exposure risk of these substances.

© 2018 Wiley Periodicals, Inc.

In plain English

This was a systematic review, not a new study. The authors searched four databases for English-language studies from January 1995 to July 2016 on workplace substances and mouth and throat cancers. They included 14 studies, mostly case-control, and described them without pooling numbers. For asbestos, three included studies reported increased risks. A French study found increased risk of hypopharyngeal cancer (odds ratio 1.80, interval 1.08 to 2.99). A Boston study of men found increased risk of pharyngeal cancer (odds ratio 1.41, interval 1.01 to 1.97). A Taiwanese study of shipbreaking workers found increased risk of oral cavity cancer (hazard ratio 2.47, interval 1.89 to 3.21) but had no smoking or alcohol data. A Dutch cohort of men found no association. Some studies also linked formaldehyde, wood dust, coal dust and welding fumes to these cancers. No study linked textile fibers to them. The authors concluded there was some evidence of associations. They added that most associations rested on only one or two studies that did not account for confounding factors, such as exposure to other substances at the same time.

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 with qualitative (non-pooled) synthesis of 14 original studies, mostly case-control studies
• Who was studied: 14 published studies (from PubMed, MEDLINE, EMBASE and ISI Web of Science, English language, January 1995 to July 2016). Six were from Europe (Sweden, France, Serbia, the Netherlands), four from the United States, two from Taiwan, one from Malaysia and one from Puerto Rico.
• Exposure: Occupational carcinogenic substances, including formaldehyde and other chemicals, asbestos, man-made vitreous fibers (such as mineral wool), wood, metal, coal, textile and leather dust, smoke and welding fumes, and building materials (cement dust and asphalt). Asbestos fiber types were not specified.
• Main results:
  • In a French case-control study (Marchand et al. 2000), asbestos was associated with increased risk of hypopharyngeal cancer: OR = 1.80 [1.08-2.99].
  • In a Boston-area case-control study of men (Langevin et al. 2013), asbestos was associated with increased risk of pharyngeal cancer: OR = 1.41 [1.01-1.97].
  • In a Taiwanese matched-cohort study of 4427 shipbreaking workers (Wu et al. 2015), asbestos was associated with increased risk of oral cavity cancer: HR = 2.47 [1.89-3.21]. The hazard ratio was adjusted only for income, with no data on smoking, alcohol or diet.
  • In the prospective Netherlands Cohort Study of 58 279 men (Offermans et al. 2014), no association was found between asbestos and oral, pharyngeal or oropharyngeal cancers.
  • In the French study, mineral wool was reported as associated with increased risk of hypopharyngeal cancer: OR = 1.55, with a printed interval of 0.99 to 2.41.
  • Across the included studies, the review reported a significant association with formaldehyde, wood dust, coal dust, asbestos and welding fumes, and a marginal association with metal and leather dust.
• The authors' conclusion: The authors concluded there is some evidence of associations between occupational substances and oral and pharyngeal cancer, particularly in the pharynx. They said better-designed studies are needed to confirm or rule out these risks.
• Limitations the authors state:
  • The search was limited to English-language publications.
  • Papers with fewer than 100 cases per anatomical site were excluded unless multiple sites were studied.
  • In most cases, the evidence for an association came from one or two studies that did not account for confounding factors such as exposure to other concomitant substances.

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: Pharyngeal Cancer, Carcinogenic, Systematic Review, Occupational Exposure, Neoplasm, Occupational Disease.

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