Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers

Our plain-English summary of Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers, by M. Boulanger, F. Morlais, V. Bouvier, et al (Occupational and Environmental Medicine, 2015).

The study

• Authors: M. Boulanger, F. Morlais, V. Bouvier, F. Galateau-Salle, L. Guittet, M.F. Marquignon, C. Paris, C. Raffaelli, G. Launoy, B. Clin
• Journal: Occupational and Environmental Medicine
• Published: 2015;72(11):792-7
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: The aim of our study was to estimate the incidence of digestive cancers within a cohort of asbestos-exposed workers.

Methods: Our study was based on a cohort of 2024 participants occupationally exposed to asbestos. The incidence of digestive cancers was calculated from 1 January 1978 to 31 December 2009 and compared with levels among the local general population using Standardised Incidence Ratios (SIRs). Asbestos exposure was assessed using the company's job-exposure matrix.

Results: 119 cases of digestive cancer were observed within our cohort, for an expected number of 77 (SIR=1.54 (1.28 to 1.85)). A significantly elevated incidence was observed for peritoneal mesothelioma, particularly in women. Significantly elevated incidences were also observed among men for: all digestive cancers, even when excluding peritoneal mesothelioma (SIR=1.50 (1.23 to 1.82)), oesophageal cancer (SIR=1.67 (1.08 to 2.47)) and liver cancer (SIR=1.85 (1.09 to 2.92)). Concerning colorectal cancer, a significant excess of risk was observed for men with exposure duration above 25 years (SIR=1.75 (1.05 to 2.73)).

Conclusions: Our results are in favour of a link between long-duration asbestos exposure and colorectal cancer in men. They also suggest a relationship between asbestos exposure and cancer of the oesophagus in men. Finally, our results suggest a possible association with small intestine and liver cancers in men.

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In plain English

This retrospective cohort study followed 2024 workers (1605 men, 419 women) employed at least a year at an asbestos textile and friction-lining plant in Calvados, Normandy, France. About two-thirds handled chrysotile only, the rest chrysotile and amphiboles. Digestive cancers diagnosed 1978 to 2009 came from the Calvados digestive cancer registry; peritoneal mesotheliomas were also recorded in the French multicentre mesothelioma registry. These were compared with numbers expected from the local population (SIR: observed divided by expected). There were 119 digestive cancers. In men, rates were significantly raised for peritoneal mesothelioma, oesophageal cancer (25 cases, SIR 1.67, 95% CI 1.08 to 2.47) and liver cancer (18 cases, SIR 1.85, 95% CI 1.09 to 2.92). Colorectal cancer in men was not significantly raised overall but was in men exposed over 25 years (19 cases, SIR 1.75, 95% CI 1.05 to 2.73). In women, only peritoneal mesothelioma was significantly raised. The authors concluded that their results favour associations with colorectal and oesophageal cancer in men, and suggest possible associations with small intestine and liver cancers in men. They noted limited statistical power, especially for women.

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: Retrospective cohort study comparing cancer incidence in the cohort with the local general population (Standardised Incidence Ratios)
• Who was studied: 2024 workers (1605 men, 419 women) of an asbestos reprocessing plant in the south of the Calvados department, Normandy, France. They were alive in 1978, had worked at least 1 year in the plant and lived in Calvados during part of the study period. Follow-up ran from 1 January 1978 to 31 December 2009.
• Exposure: Occupational asbestos exposure in textile and friction-lining production. Workers handled either chrysotile only (1320, 65.2%) or both chrysotile and amphiboles (704, 34.8%). Exposure was estimated with a company-specific job-exposure matrix in three ways: a Cumulative Exposure Index (fibres/mL×years), exposure duration, and mean exposure level. Each was split at its median: 80 fibres/mL×years, 25 years and 4 fibres/mL.
• Main results:
  • 119 digestive cancers were registered in the cohort from 1978 to 2009; 89% were in men and 11% in women.
  • Men: incidence was significantly elevated for peritoneal mesothelioma, liver cancer, oesophageal cancer, and all digestive cancers combined, with or without peritoneal mesothelioma. Oesophageal cancer: 25 observed vs 14.9 expected, SIR 1.67 (1.08 to 2.47). Liver cancer: 18 observed vs 9.75 expected, SIR 1.85 (1.09 to 2.92). All digestive cancers excluding mesothelioma: 103 observed vs 68.5 expected, SIR 1.50 (1.23 to 1.82).
  • Women: the only site with a significant excess was peritoneal mesothelioma, with 5 observed vs 0.12 expected, SIR 43.0 (13.9 to 100).
  • Colorectal cancer in men overall was not significantly elevated: 33 observed vs 25.9 expected, SIR 1.27 (0.87 to 1.79). It was significantly elevated in men exposed for more than 25 years: 19 observed vs 10.9 expected, SIR 1.75 (1.05 to 2.73). By cumulative exposure, the colorectal SIR in the highest group of men was elevated but not significant.
  • Oesophageal cancer was also significantly elevated in men with cumulative exposure above 80 fibres/mL×years: 20 observed, SIR 1.90 (1.16 to 2.94).
  • Small intestine cancer in men was significantly elevated in two groups, each based on 3 cases: the highest mean-exposure-level group, SIR 5.88 (1.18 to 17.2), and the highest cumulative exposure group, SIR 6.50 (1.31 to 19.0). The overall SIR in men, 4.47 (0.90 to 13.1), was not statistically significant.
  • Liver cancer in men was significantly elevated in the highest cumulative exposure group, SIR 2.18 (1.22 to 3.59), and the highest mean exposure level group, SIR 2.26 (1.31 to 3.61). By duration, however, the excess was significant only in men with the shorter exposure duration (11 cases). The authors found no explanation for this.
• The authors' conclusion: The authors concluded that their study provides new data in favour of an association between asbestos exposure and colorectal cancer in men, and that they observed an association for oesophageal cancer in men. They stated that their results suggest potential associations for small intestine cancer and liver cancer, both in men.
• Limitations the authors state:
  • The study lacked statistical power, particularly for women.
  • There were no data on the main confounding factors, such as alcohol, tobacco, diet and body mass index. The authors could not formally verify that the local reference population was similar to the cohort on these factors.
  • The small intestine findings rested on only 3 cases in men and could be due to chance.
  • The authors said the liver cancer results should be considered with caution and investigated by studies with appropriate design.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Standardized Incidence Ratio (SIR), Peritoneal Mesothelioma, Esophageal Cancer, Colorectal Cancer.

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• Cancer incidence within a cohort occupationally exposed to asbestos: a study of dose--response relationships — B. Clin, F. Morlais, et al. (2011)
• Cancer incidence in a chlorochemical plant in Isère, France: an occupational cohort study, 1979-2002 — V. Bonneterre, G. Mathern, et al. (2012)
• Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort — S. Lin, X. Wang, et al. (2014)

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