Asbestos Exposure and Increased Risk of Intrahepatic Cholangiocarcinoma: Enough to Infer Causality?

Our plain-English summary of Asbestos Exposure and Increased Risk of Intrahepatic Cholangiocarcinoma: Enough to Infer Causality?, by C. La Vecchia, M. Lotti, M. Colombo (Gastroenterology, 2020).

The study

• Authors: C. La Vecchia, M. Lotti, M. Colombo
• Journal: Gastroenterology
• Published: 2020;159(2):794-795
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This article was not a new study but a short commentary in which the authors discussed a review by Brandi and Tavolari (Cells, 2020) on occupational asbestos exposure and intrahepatic cholangiocarcinoma (iCCA), a cancer of the bile ducts inside the liver. The review's authors suggested asbestos be listed as a possible risk factor for iCCA. The commentary said the review relied partly on 15 cohort studies, most of which did not separate liver from biliary tract cancers, and called those results inconsistent. It described two case-control studies as more informative. In an Italian study, self-reported asbestos exposure was associated with iCCA (odds ratio 4.8, 95% CI 1.7-13.3), with no significant association for extrahepatic cholangiocarcinoma (eCCA). In a Nordic study, the odds ratio for iCCA was 1.2 for ever exposure (borderline significance) and 1.7 (95% CI 1.1 to 2.5) at the highest exposure level, with no association for eCCA. The authors pointed to approximate exposure assessment, possible misclassification of liver metastases as iCCA, and moderate excess risks open to bias and confounding. They concluded the question remains undefined and unquantified.

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: Commentary (a 'Selected Summary') on a published review by Brandi and Tavolari (Cells 2020); no new data were collected
• Who was studied: The commented-on review gathered case reports, cohort studies and case-control studies on occupational asbestos exposure and biliary cancer; the commentary discussed in particular an Italian case-control study and a Nordic (NOCCA) nested case-control study
• Exposure: Occupational exposure to asbestos (fiber types not specified); in the Italian study, exposure was self-reported
• Main results:
  • According to the commentary, the review based the potential for asbestos to cause biliary tumours on an excess risk of liver/biliary tract cancers in exposed workers from 15 cohort studies. Most of those studies did not separate liver from biliary tract cancers.
  • The commentary's authors described the cohort findings in the review's Table 2 as inconsistent. The association was significant in about half of the studies.
  • Italian case-control study (Brandi et al. 2013; 41 iCCA cases and 149 controls, plus 59 eCCA cases and 212 controls): self-reported asbestos exposure was significantly associated with iCCA, with an odds ratio of 4.8 (95% CI 1.7-13.3).
  • In the same Italian study, no significant association was found for eCCA (OR 2.09; the confidence interval is not given in the text).
  • Nordic NOCCA nested case-control study (Farioli et al. 2018; 1458 iCCA cases and 3972 eCCA cases): for iCCA, the odds ratio was 1.2 for ever exposure, of borderline significance, rising to 1.7 (95% CI 1.1 to 2.5) at the highest exposure level.
  • In the Nordic study, there was no association with eCCA.
  • The review cited studies finding asbestos fibers in bile and biliary epithelium. The commentary said these studies do not show what dose is associated with iCCA.
• The authors' conclusion: The authors concluded that only vague inferences about causality can be made. They wrote that the issue of asbestos exposure and iCCA risk remains undefined and unquantified.
• Limitations the authors state:
  • Asbestos exposure in the studies was assessed by self-report and questionnaires, without direct measurements, and so is necessarily approximate
  • Diagnoses of iCCA may include liver metastases misclassified as iCCA
  • The excess risks are moderate, so bias and confounding in observational studies could partly or largely explain the apparent association
  • The absence of an association with the more common eCCA does not support a role for asbestos in biliary tract cancer

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure.

Related studies

• Exposure to Asbestos and Increased Intrahepatic Cholangiocarcinoma Risk: Growing Evidences of a Putative Causal Link — G. Brandi, K. Straif, et al. (2022)
• Asbestos exposure as an additional risk factor for small duct intrahepatic cholangiocarcinoma: a pilot study — F. Vasuri, M. Deserti, et al. (2023)
• New insights into the molecular pathogenesis of intrahepatic cholangiocarcinoma — T. Patel (2014)
• Asbestos and Intrahepatic Cholangiocarcinoma — G. Brandi, S. Tavolari (2020)
• Intrahepatic cholangiocarcinoma development in a patient with a novel BAP1 germline mutation and low exposure to asbestos — G. Brandi, M. Deserti, et al. (2020)
• Occupational exposure to asbestos and risk of cholangiocarcinoma: a population-based case-control study in four Nordic countries — A. Farioli, K. Straif, et al. (2018)

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