Asbestos and gastrointestinal cancer. A review of the literature

Our plain-English summary of Asbestos and gastrointestinal cancer. A review of the literature, by R.W. Morgan, D.E. Foliart, O. Wong (The Western Journal of Medicine, 1985).

The study

• Authors: R.W. Morgan, D.E. Foliart, O. Wong
• Journal: The Western Journal of Medicine
• Published: 1985;143(1):60-5
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M nos. 000492, 002790).

Abstract

Exposure to asbestos is among several factors cited as possible causes of esophageal, gastric and colorectal cancer. More than 45 published studies have presented mortality data on asbestos-exposed workers. For each cohort, we listed the observed and expected rates of deaths from types of gastrointestinal cancer based on the latest published follow-up. Summary standardized mortality ratios (SMRs) were then derived. Finally, we calculated summary SMRs for total gastrointestinal tract cancer for three occupational groups: asbestos factory workers, insulators/shipyard workers and asbestos miners. Statistically significant elevations in summary SMRs were found for esophageal, stomach and total gastrointestinal tract cancer in all asbestos-exposed workers. Esophageal cancer summary SMRs remained significantly elevated when data were reanalyzed to include only those cohorts with death certificate diagnoses for cause of observed deaths. However, summary SMRs were not statistically significant for stomach and total gastrointestinal tract cancer after reanalysis. Summary SMRs by occupational group showed a significant elevation for total gastrointestinal cancer in insulators/shipyard workers. The elevation was not significant after reanalysis. Based on the results after reanalysis, the elevations in summary SMRs for stomach and total gastrointestinal tract cancer are of a magnitude that could result from diagnostic and investigator error. We conclude that more studies are required before stomach and colorectal cancers are documented as asbestos-related diseases.

In plain English

This 1985 review examined published mortality studies of asbestos-exposed workers for esophageal, stomach and colorectal cancer. Peritoneal mesothelioma was not reviewed, and mesothelioma deaths were removed from gastrointestinal counts only where studies gave separate numbers. The authors found some 45 publications on about 22 overlapping worker groups and pooled observed and expected deaths into summary standardized mortality ratios (SMRs). Across all exposed workers, summary SMRs were significantly elevated: 214 for esophageal cancer (21 deaths observed, 9.8 expected), 183 for stomach and 108 for total gastrointestinal cancer. Colorectal cancer (SMR 113) was not. Some cause-of-death data came from "best evidence" rather than death certificates. When those data were removed, esophageal cancer stayed significantly elevated (SMR 238), but stomach and total gastrointestinal cancer did not. By occupation, only insulators/shipyard workers had a significant excess of total gastrointestinal cancer (SMR 132), which was not significant after the same removal. The authors were not convinced of a relationship to asbestos, especially for stomach cancer. They noted that negative studies were less likely to report SMRs or observed and expected deaths. Studies negative for gastrointestinal cancer but positive for respiratory cancer would still likely be published.

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: Literature review of published cohort mortality studies of asbestos-exposed workers, with deaths pooled into summary standardized mortality ratios. Peritoneal mesothelioma was not reviewed.
• Who was studied: Asbestos-exposed worker groups described in published studies: some 45 publications covering about 22 partly overlapping cohorts
• Exposure: Occupational asbestos exposure, analysed for all exposed workers together and separately for asbestos factory workers, insulators/shipyard workers and asbestos miners
• Main results:
  • All exposed workers: esophageal cancer summary SMR 214 (21 observed, 9.8 expected; 95% confidence interval 132.6-327.6) and stomach cancer summary SMR 183 (43 observed, 23.5 expected; 95% confidence interval 132.4-246.5), both significantly elevated
  • All exposed workers: colorectal cancer summary SMR 113 (176 observed, 156.4 expected; 95% confidence interval 96.5-130.4), not statistically significant
  • All exposed workers: total gastrointestinal tract cancer summary SMR 108 (912 observed, 840.9 expected; 95% confidence interval 101.5-115.7), minimally but significantly elevated
  • After removing "best evidence" data: esophageal cancer remained significantly elevated, SMR 238 (20 observed, 8.4 expected; 95% confidence interval 145-368)
  • After removing "best evidence" data: stomach cancer SMR 133 (24 observed, 18.1 expected; 95% confidence interval 85-197) and total gastrointestinal tract cancer SMR 105 (869 observed, 825.8 expected; 95% confidence interval 98-113) were not statistically significant
  • By occupation: only insulators/shipyard workers had a significant elevation in total gastrointestinal tract cancer, SMR 132 (203 observed, 153.5 expected; 95% confidence interval 114.7-151.7). Asbestos factory workers had SMR 105 (95% confidence interval 95.9-115.4) and asbestos miners had SMR 99 (95% confidence interval 87.4-112.5)
  • Insulators/shipyard workers after removing "best evidence" data: total gastrointestinal tract cancer SMR 116 (160 observed, 138.4 expected; 95% confidence interval 98.0-135.0), not significantly elevated
• The authors' conclusion: The authors stated they were not convinced of a relationship between the elevations and asbestos exposure, especially for stomach cancer, where they judged the finding inconsistent and possibly erroneous in the largest positive study
• Limitations the authors state:
  • Negative studies were less likely to result in published SMRs or observed and expected deaths, and the authors knew of no way to correct for this bias. They added that studies negative for gastrointestinal cancer but positive for respiratory tract cancer would still have a high likelihood of being published.
  • For esophageal and stomach cancer the numbers of deaths were small and the confidence intervals wide
  • Causes of death may be misdiagnosed or wrongly certified; some gastrointestinal cancers are certified as mesothelioma and vice versa
  • Some included studies grouped peritoneal mesothelioma deaths with gastrointestinal cancers. The authors removed these only when the actual numbers of mesotheliomas were given.
  • In some included studies, the gastrointestinal cancer figures include mesotheliomas

Topics

Medical terms in this study, explained in our Lexicon: Colorectal Cancer, standardized mortality ratio (SMR), Insulator, Esophageal Cancer, Death Certificate.

Related studies

• Gastrointestinal cancer mortality of workers in occupations with high asbestos exposures — S.K. Kang, C.A. Burnett, et al. (1997)
• Asbestos exposure and lymphomas of the gastrointestinal tract and oral cavity — R. Ross, R. Dworsky, et al. (1982)
• Does asbestos exposure cause gastrointestinal cancer? — D.S. Levine (1985)
• Re: Meta-analysis of asbestos and gastrointestinal cancer — R.W. Morgan (1991)
• Assessing Tumor-Infiltrating Lymphocytes in Solid Tumors: A Practical Review for Pathologists and Proposal for a Standardized Method from the International Immuno-Oncology Biomarkers Working Group: Part 2: TILs in Melanoma, Gastrointestinal Tract Carcinomas, Non-Small Cell Lung Carcinoma and Mesothelioma, Endometrial and Ovarian Carcinomas, Squamous Cell Carcinoma of the Head and Neck, Genitourinary Carcinomas, and Primary Brain Tumors — S. Hendry, R. Salgado, et al. (2017)
• Simple nutritional intervention in patients with advanced cancers of the gastrointestinal tract, non-small cell lung cancers or mesothelioma and weight loss receiving chemotherapy: a randomised controlled trial — C. Baldwin, A. Spiro, et al. (2011)

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