Incidence of digestive cancers and occupational exposure to asbestos

Our plain-English summary of Incidence of digestive cancers and occupational exposure to asbestos, by S. de La Provôté, N. Desoubeaux, C. Paris, et al (European Journal of Cancer Prevention, 2002).

The study

• Authors: S. de La Provôté, N. Desoubeaux, C. Paris, M. Letourneux, C. Raffaelli, F. Galateau-Salle, M. Gignoux, G. Launoy
• Journal: European Journal of Cancer Prevention
• Published: 2002;11(6):523-8
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

While the role of exposure to asbestos in the development of several cancers such as mesotheliomas and bronchopulmonary cancers is now well established, the possible relationship between digestive cancers, other than peritoneal mesotheliomas, and occupational exposure to asbestos is still controversial. The great majority of the studies are based on mortality data. The aim of the study was to analyse the relationship between digestive cancer incidence and occupational exposure to asbestos in a population of subjects for whom precise occupational exposure data and precise incidence data were available. The population consisted of salaried and retired workers from a company using asbestos to manufacture fireproof textiles and friction materials. There were 1454 men (79.9%) and 366 women (20.1%). A cumulative exposure index and a mean exposure concentration in fibres/ml for each subject were calculated with the aid of an in-house job-exposure matrix. The number of cases of digestive cancer observed was compared with the expected and Standardized Incidence Ratio (SIR) was estimated. Precise occupational exposure data allowed us to study the dose-response relationship between asbestos exposure and risk of digestive cancer using Cox model. Fifty-six digestive cancers occurred in the study population over the 18-year follow-up period for 48.4 expected (SIR = 1.16 [0.87-1.50]). Comparing with incidence in the county, SIR was not significant for any of the digestive localization, but for peritoneum. However, even after taking into account the potential confounders via the Cox model, there was a significant dose-response relationship between the occurrence of digestive cancers and the mean exposure concentration, even after exclusion of peritoneum cancers. Our study provides initial evidence suggesting a relationship between occupational exposure to asbestos and the risk of digestive cancer: first, it is a study of incidence although the risk evidenced is not significant; secondly, a dose-effect relationship is demonstrated in the whole population. However, these preliminary results require confirmation by more powerful studies focusing on larger series.

In plain English

This French study followed 1,820 current and retired workers (1,454 men and 366 women) of a company in the Calvados department that used asbestos to make fireproof textiles and friction materials. Workers handled chrysotile alone or chrysotile mixed with crocidolite. Using the local digestive cancer registry, the authors counted digestive cancers diagnosed from 1978 to 1995 and compared them with rates in Calvados. There were 56 digestive cancers against 48.4 expected (SIR 1.16, 95% CI 0.87 to 1.50), an excess that was not statistically significant. Peritoneal cancers, all mesotheliomas, were significantly in excess: 4 observed against 0.3 expected (SIR 13.3, 95% CI 3.59 to 34.14). In a model adjusted for age at recruitment and latency, risk rose with mean exposure concentration (hazard ratio 6.10, 95% CI 1.46 to 25.51, highest group versus under 3 fibres/ml). The pattern held after excluding peritoneal cases. The authors concluded this was initial evidence suggesting a link, needing confirmation in larger studies. They noted limited statistical power and missing data on workers who died before 1978.

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: Cohort study of cancer incidence. Observed cancers were compared with those expected from county registry rates (standardized incidence ratios). Dose-response was analysed with a Cox proportional hazards model.
• Who was studied: 1,820 salaried and retired workers (1,454 men, 366 women) of an asbestos-using company in the south of the Calvados department, France. All had worked at least one year at the company, lived in Calvados, and were alive in 1978. They were followed from 1978 to 1995, totalling 27,734 person-years. 152 workers were not included because their address or vital status was unknown.
• Exposure: Occupational asbestos exposure in the manufacture of fireproof textiles and friction materials. Workers were exposed to chrysotile alone (n = 1174) or to mixed chrysotile and crocidolite (n = 646). Each worker's exposure was estimated with an in-house job-exposure matrix. The mean cumulative exposure index was 138.6 fibres/ml years and the mean exposure concentration was 7.8 fibres/ml.
• Main results:
  • In the whole cohort, 56 digestive cancers (49 in men, 7 in women) were diagnosed between 1978 and 1995, against 48.4 expected.
  • All digestive cancers combined, compared with Calvados rates: SIR 1.16 (95% CI 0.87 to 1.50), not statistically significant.
  • Peritoneum: 4 cancers observed against 0.3 expected, SIR 13.3 (95% CI 3.59 to 34.14). This was a significant excess (p less than 0.001), and all four cases were mesotheliomas.
  • Digestive cancers excluding the peritoneum: 52 observed against 47.5 expected, SIR 1.09 (95% CI 0.82 to 1.44), not significant. No individual digestive site other than the peritoneum showed a significant excess. For example, oesophagus had 16 observed against 12.4 expected (SIR 1.29) and colon-rectum had 18 observed against 17.9 expected (SIR 1.01).
  • In the Cox model adjusted for age at recruitment and latency, digestive cancer risk was associated with mean exposure concentration. Compared with workers below 3 fibres/ml, the adjusted hazard ratio was 3.21 (95% CI 0.74 to 13.96) for 3 to 9 fibres/ml and 6.10 (95% CI 1.46 to 25.51) for the highest category (9 fibres/ml upward). The trend test gave p less than 0.05.
  • The dose-response results showed the same pattern after peritoneal cases were excluded.
  • In the unadjusted analysis, risk was higher in workers with mixed chrysotile and crocidolite exposure than in those exposed to chrysotile alone (crude hazard ratio 2.20, 95% CI 1.29 to 3.73). Fibre type was not included in the final model. Risk did not increase with number of years in the company.
  • No significant dose-response relationship was found for oesophageal cancer, and no dose-response relationship was found for colorectal cancer.
• The authors' conclusion: The authors concluded that their study provides initial evidence suggesting a relationship between occupational asbestos exposure and digestive cancer risk. They noted that the excess risk was not significant but a dose-effect relationship was seen, and that these preliminary results require confirmation in larger studies.
• Limitations the authors state:
  • The study lacked statistical power. It also had no cancer incidence data before 1978, so workers who died before then were excluded. The authors say this may have caused selection bias and could have led to an underestimated SIR.
  • There was no information on workers who died or moved out of Calvados before 1978.
  • The precise amount of exposure due to amphiboles alone was not available.
  • The study was too small to test whether there is a threshold in duration of exposure.
  • For oesophageal cancer, strong risk factors such as alcohol, tobacco and eating habits mean a larger population would probably be needed to show any role of asbestos.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Mesothelioma, Peritoneal Mesothelioma, Cumulative Exposure, Standardized Incidence Ratio (SIR), Dose-response relationship, Asbestos Exposure, Peritoneum.

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• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)
• Asbestos exposure, pleural plaques and digestive cancers — B. Clin, C. Gramond, et al. (2025)
• Cancer incidence within a cohort occupationally exposed to asbestos: a study of dose--response relationships — B. Clin, F. Morlais, et al. (2011)
• A graphical analysis of the interrelationships among waterborne asbestos, digestive system cancer and population density — M.E. Tarter, R.C. Cooper, et al. (1983)
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