Cancer of the esophagus and asbestos exposure

Our plain-English summary of Cancer of the esophagus and asbestos exposure, by B. Clin, I. Thaon, M. Boulanger, et al (American Journal of Industrial Medicine, 2017).

The study

• Authors: B. Clin, I. Thaon, M. Boulanger, P. Brochard, S. Chamming's, A. Gislard, A. Lacourt, A. Luc, G. Ogier, C. Paris, J.C. Pairon
• Journal: American Journal of Industrial Medicine
• Published: 2017;60(11):968-975
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Our study aimed at analyzing incidence and mortality from esophageal cancer within a cohort of workers with previous occupational asbestos exposure (ARDCo Program).

Methods: A 10-year follow-up study was conducted in the 14 515 male subjects included in this program between October 2003 and December 2005. Follow-up began when exposure stopped. Asbestos exposure was analyzed by industrial hygienists using data from a standardized questionnaire. The Cox model was used, with age as the time axis variable adjusted for smoking, time since first exposure (TSFE) and cumulative exposure index (CEI) of exposure to asbestos.

Results: We reported a significant dose-response relationship between CEI of exposure to asbestos and esophageal cancer, in both incidence (hazard ratio [HR] 1.26, 95% confidence interval [CI] 1.00-1.58), and mortality (HR 1.40, [95%CI 1.12-1.75]).

Conclusions: This large-scale study suggests the existence of a relationship between asbestos exposure and cancer of the esophagus.

© 2017 Wiley Periodicals, Inc.

In plain English

This French study followed 14,515 men in the Asbestos-Related Diseases Cohort (ARDCo). They came from a screening program for retired or unemployed workers formerly exposed to asbestos at work, enrolled in four regions from October 2003 to December 2005. Industrial hygienists rated each man's exposure in every job from a standardized questionnaire, calculated a cumulative exposure index, and classified 656 men (4.5%) as non-exposed. The article did not specify this cohort's fiber types. Over about 10 years, 31 new esophageal cancers were recorded through national health insurance, and 33 men died of esophageal cancer by the end of 2012. After adjusting for smoking and time since first exposure, higher cumulative exposure (on a logarithmic scale) was associated with esophageal cancer incidence (hazard ratio 1.26, 95% CI 1.00-1.58) and mortality (hazard ratio 1.40, 95% CI 1.12-1.75). The authors concluded the study suggests a relationship between asbestos exposure and esophageal cancer and called for larger studies to confirm it. They noted they lacked tumor-type, detailed smoking and alcohol data, and that insurance records may have missed cases.

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: Prospective cohort study with about 10 years of follow-up for cancer incidence and mortality, analyzed with Cox proportional hazards models
• Who was studied: 14,515 men in the Asbestos-Related Diseases Cohort (ARDCo). The cohort came from a screening program for retired or unemployed workers formerly exposed to asbestos at work and covered by French National Health Insurance. Participants enrolled between October 2003 and December 2005 in four French regions: Aquitaine, Upper Normandy, Lower Normandy and Rhône-Alpes. After hygienist assessment, 656 men (4.5%) were classified as non-exposed. Mean age at baseline was 63.2 years. Incidence follow-up ran to April 4, 2015, and causes of death were available up to December 31, 2012. The mortality analysis included 13,055 men.
• Exposure: Occupational asbestos exposure; the article does not specify the fiber types for this cohort. Industrial hygienists assessed exposure from a standardized questionnaire covering every job held. Each job was given one of four levels (0.01, 0.1, 1 or 10 equivalent fibers/mL), and that level was multiplied by the job's duration in years. These were summed into a cumulative exposure index in fibers.years/mL. Mean cumulative exposure index was 60.1 f.years/mL, and mean exposure duration was 30.9 years. 656 men (4.5%) were judged non-exposed after hygienist review.
• Main results:
  • Incidence: 31 cancers of the esophagus were recorded in the cohort. In the multivariable model adjusted for smoking and time since first exposure, the cumulative exposure index (on a log scale) showed a significant dose-response with esophageal cancer incidence: HR 1.26 (95% CI 1.00-1.58), P = 0.05. The unadjusted HR was 1.13 (95% CI 0.92-1.38).
  • Mortality: 33 men died of cancer of the esophagus between the start of the study and December 31, 2012.
  • Mortality, single-factor analysis (13,055 men): the cumulative exposure index was significantly associated with death from esophageal cancer, HR 1.28 (95% CI 1.04-1.57).
  • Mortality, multivariable analysis adjusted for smoking status and time since first exposure: the association with the cumulative exposure index was confirmed, HR 1.40 (95% CI 1.12-1.75), P = 0.003.
  • For esophageal cancer incidence, a significant negative association was observed with time since first exposure, in both univariate and multivariate analyses.
  • Smoking status was significantly related to esophageal cancer in single-factor analyses.
  • Results were comparable after excluding men with no smoking information, in both the incidence and the mortality analyses.
• The authors' conclusion: The authors concluded that this large-scale study suggests a relationship between asbestos exposure and cancer of the esophagus. They said studies with greater statistical power are needed to confirm the observed associations.
• Limitations the authors state:
  • No information was available on the histological types of esophageal cancer.
  • There were too few incident cases to give statistical power to study particular cancer subtypes.
  • Smoking was adjusted for only in broad categories, with no pack-years, which could leave residual confounding.
  • Alcohol consumption, a potential confounding factor, could not be taken into account.
  • Some people with esophageal cancer may not have requested full insurance coverage, so cases may have been missed. The authors said this misclassification could have weakened the association seen in the incidence study.
  • Nearly all esophageal cancer deaths occurred 40 or more years after first exposure, so no clear conclusion could be drawn about time since first exposure.

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: Esophageal Cancer, Asbestos Exposure, Cumulative Exposure, Dose-response relationship, Hazard Ratio, confidence interval.

Related studies

• Asbestos exposure, pleural plaques and digestive cancers — B. Clin, C. Gramond, et al. (2025)
• Esophagus cancer and occupational exposure to asbestos: results from a meta-analysis of epidemiology studies — B. Li, S.P. Tang, et al. (2016)
• Occupational Asbestos Exposure and Incidence of Colon and Rectal Cancers in French Men: The Asbestos-Related Diseases Cohort (ARDCo-Nut) — C. Paris, I. Thaon, et al. (2017)
• Pleural plaques and the risk of pleural mesothelioma — J.C. Pairon, F. Laurent, et al. (2013)
• Occupations and industries in France at high risk for pleural mesothelioma: A population-based case-control study (1998-2002) — P. Rolland, C. Gramond, et al. (2010)
• Asbestos exposure, pleural plaques, and the risk of death from lung cancer — J.C. Pairon, P. Andujar, et al. (2014)

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