Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: results of a case-control study

Our plain-English summary of Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: results of a case-control study, by J.L. Marchand, D. Luce, A. Leclerc, et al (American Journal of Industrial Medicine, 2000).

The study

• Authors: J.L. Marchand, D. Luce, A. Leclerc, P. Goldberg, E. Orlowski, I. Bugel, J. Brugère
• Journal: American Journal of Industrial Medicine
• Published: 2000;37(6):581-9
• Cited by: 44 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The data from a case-control study performed in France between 1989 and 1991 were used to test whether exposure to either asbestos or to man-made vitreous fibers (MMVF) is a risk factor for cancer of the larynx or the hypopharynx.

Methods: This study involved 315 incident cases of laryngeal cancer, 206 cases of hypopharyngeal cancer, and 305 hospital-based controls with other types of cancer, all recruited in 15 hospitals in six French cities. The subjects' past occupational exposure to asbestos and to four types of MMVF (mineral wool, refractory ceramic fibers, glass filaments, and microfibers) was evaluated based on their job history, with the aid of a job-exposure matrix. Odds ratios were calculated with unconditional logistic regression, with adjustment for smoking and drinking levels.

Results: Exposure to asbestos resulted in a significant increase in the risk of hypopharyngeal cancer (OR = 1.80, 95% CI: 1.08-2.99) and a nonsignificant increase in the risk of laryngeal cancer (OR = 1.24, 95% CI: 0.83-1.90). Risk was highest for the epilarynx (highest cumulative level of exposure: OR = 2.22, 95% CI: 1.05-4.71). Exposure to mineral wools was of borderline significance for the risk of hypopharyngeal cancer (OR = 1.55, 95% CI: 0.99-2.41), and nonsignificantly associated with the risk of laryngeal cancer (OR-1.33, 95% CI: 0.91-1.95). The risk was again highest for the epilarynx (OR = 1.85, 95% CI: 1.08-3.17). No significant results were observed for the other MMVF.

Conclusions: These results suggest that asbestos exposure increases the risk of epilaryngeal and hypopharyngeal cancers. It is difficult to reach a conclusion about the effects of mineral wools, because nearly all the exposed subjects were also exposed to asbestos. The possible effects of other MMVF were difficult to assess in this study, because of the paucity of exposed subjects.

Copyright 2000 Wiley-Liss, Inc.

In plain English

This was a case-control study in France, run from 1989 to 1991 in 15 hospitals in six cities. It compared men newly diagnosed with squamous cell cancer of the larynx or hypopharynx with men who had other, nonrespiratory cancers. Each man's past exposure at work to asbestos and to four man-made vitreous fibers (mineral wools, refractory ceramic fibers, glass filaments, microfibers) was estimated from his job history using a job-exposure matrix. Results were adjusted for age, smoking and alcohol. Ever exposure to asbestos was linked to a statistically significant increase in hypopharyngeal cancer (OR 1.80, 95% CI 1.08 to 2.99) and a non-significant increase in laryngeal cancer (OR 1.24, 0.83 to 1.90). Within the larynx, the highest cumulative asbestos level was linked to epilaryngeal cancer (OR 2.22, 1.05 to 4.71). Mineral wool results pointed the same way, but nearly all men exposed to mineral wools were also exposed to asbestos. Too few men were exposed to the other fibers to judge their effects. The authors concluded that asbestos exposure suggests an increased risk of hypopharyngeal cancer.

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: Hospital-based case-control study; exposure assigned from job histories with a job-exposure matrix; odds ratios from unconditional logistic regression
• Who was studied: Men newly diagnosed with squamous cell carcinoma of the larynx or hypopharynx from 1 January 1989 to 1990–1991 in 15 hospitals in six French cities. Controls were men with other (nonrespiratory) cancers from the same hospitals. 528 cases and 305 controls were included. The analyses covered 296 laryngeal cancer cases, 201 hypopharyngeal cancer cases and 295 controls.
• Exposure: Occupational exposure to asbestos (fiber type not specified) and to four man-made vitreous fibers: mineral wools, refractory ceramic fibers, glass filaments and microfibers. Exposure was estimated with a job-exposure matrix that gave probability, concentration and frequency of exposure for each job. It was summarized as ever/never exposure and as cumulative level (low, intermediate, high). Environmental exposure was not counted.
• Main results:
  • Ever exposure to asbestos: for laryngeal cancer, OR 1.24 (95% CI 0.83 to 1.90), not statistically significant; for hypopharyngeal cancer, OR 1.80 (95% CI 1.08 to 2.99), statistically significant.
  • Hypopharyngeal cancer, highest cumulative asbestos exposure level: OR 2.14 (95% CI 1.14 to 4.01). For laryngeal cancer, risk rose with cumulative exposure, but the odds ratios did not differ significantly from 1.
  • With a 15-year lag in the exposure calculations, the asbestos odds ratio was 1.40 (95% CI 0.94 to 2.08) for laryngeal cancer and 2.07 (95% CI 1.25 to 3.43) for hypopharyngeal cancer.
  • Larynx subsites: epilaryngeal cancer was significantly associated with a high cumulative level of asbestos exposure (OR 2.22, 95% CI 1.05 to 4.71). No significant association was seen for the other larynx subsites. Hypopharyngeal and epilaryngeal cancers grouped together: OR 1.77 (95% CI 1.13 to 2.76).
  • Smoking and asbestos: the results did not support a stronger asbestos effect among smokers. The interaction terms were not significant (larynx P 0.59; hypopharynx P 0.53).
  • Ever exposure to mineral wools: for laryngeal cancer, OR 1.33 (95% CI 0.91 to 1.95), not significant; for hypopharyngeal cancer, OR 1.55 (95% CI 0.99 to 2.41), borderline significance; for epilaryngeal cancer, OR 1.85 (95% CI 1.08 to 3.17), significant.
  • Very few subjects were exposed only to mineral wools and not to asbestos. When both exposures were in the same model, the odds ratios for asbestos and for mineral wools both decreased.
  • No significant association was observed between either cancer and exposure to ceramic fibers, glass filaments or microfibers, but few subjects had these exposures.
• The authors' conclusion: The authors concluded that their results suggest asbestos exposure increases the risk of hypopharyngeal cancer, with the excess risk in the larynx higher for epilaryngeal cancer, and that asbestos may have a carcinogenic effect on the epilarynx and hypopharynx. They stated that mineral wool findings must be interpreted cautiously because of possible confounding by asbestos, and that too few subjects were exposed to the other synthetic fibers for valid conclusions.
• Limitations the authors state:
  • Estimating past exposure caused non-negligible misclassification. The authors argue this was non-differential and would tend to bias odds ratios toward 1.
  • Nearly all subjects exposed to mineral wools were also exposed to asbestos, so residual confounding by asbestos cannot be excluded.
  • Mineral wool exposure levels in the job-exposure matrix may be less reliable than for asbestos, so cumulative mineral wool results were not presented.
  • Too few subjects were exposed to ceramic fibers, glass filaments or microfibers for any effect to be detected.
  • Some controls had cancers (stomach, colon-rectum, pancreas) that some studies have linked to asbestos, which might weaken the associations. These were 16% of controls, and excluding them did not change the main results.

Topics

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

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Vitreous, Case-Control Study, Laryngeal Cancer, Odds Ratio, Asbestos Exposure.

Related studies

• Occupational exposure and laryngeal and hypopharyngeal cancer risk in central and eastern Europe — O. Shangina, P. Brennan, et al. (2006)
• Risk of lung cancer associated with occupational exposure to mineral wools: updating knowledge from a french population-based case-control study, the ICARE study — F. Guida, S. Paget-Bailly, et al. (2013)
• Investigation on the durability of man-made vitreous fibers in rat lungs — B. Bellmann, H. Muhle, et al. (1994)
• Mortality among a cohort of US man-made mineral fiber workers: 1985 follow-up — G.M. Marsh, P.E. Enterline, et al. (1990)
• Occupation and larynx and hypopharynx cancer: a job-exposure matrix approach in an international case-control study in France, Italy, Spain and Switzerland — F. Berrino, L. Richiardi, et al. (2003)
• Pleural mesothelioma and occupational coexposure to asbestos, mineral wool, and silica — A. Lacourt, C. Gramond, et al. (2013)

Browse more research in American Journal of Industrial Medicine, or return to medical research.