Objectives To assess the association between occupational exposure to asbestos and the risk of cholangiocarcinoma (CC).
Methods We conducted a case–control study nested in the Nordic Occupational Cancer (NOCCA) cohort. We studied 1458 intrahepatic CC (ICC) and 3972 extrahepatic CC (ECC) cases occurring among subjects born in 1920 or later in Finland, Iceland, Norway and Sweden. Each case was individually matched by birth year, gender and country to five population controls. The cumulative exposure to asbestos (measured in fibres (f)/ml × years) was assessed by applying the NOCCA job-exposure matrix to data on occupations collected during national population censuses (conducted in 1960, 1970, 1980/81 and 1990). Odds ratios (OR) and 95% CI were estimated using conditional logistic regression models adjusted by printing industry work.
Results We observed an increasing risk of ICC with cumulative exposure to asbestos: never exposed, OR 1.0 (reference category); 0.1–4.9 f/mL × years, OR 1.1 (95% CI 0.9 to 1.3); 5.0–9.9 f/mL × years, OR 1.3 (95% CI 0.9 to 2.1); 10.0–14.9 f/mL × years, OR 1.6 (95% CI 1.0 to 2.5); ≥15.0 f/mL × years, OR 1.7 (95% CI 1.1 to 2.6). We did not observe an association between cumulative asbestos exposure and ECC.
Conclusions Our study provides evidence that exposure to asbestos might be a risk factor for ICC. Our findings also suggest that the association between ECC and asbestos is null or weaker than that observed for ICC. Further studies based on large industrial cohorts of asbestos workers and possibly accounting for personal characteristics and clinical history are needed.
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Contributors EP, KS and SM contributed to the conception of the study. AF, EP, FSV, GBi, GBr, JIM, KS, SC and SM contributed to the design of the study. EP, EW, JIM, KK, LT and PS contributed to the collection of data. AF, JIM, SC and SM contributed to the analysis of data. AF, EP, FSV, GBr, KS, SC and SM contributed to the interpretation of data. AF, FSV, GBr, SC and SM contributed to drafting the article. EP, EW, GBi, JIM, KK, KS, LT and PS contributed to the critical revision of the article. All authors read and approved the final version of the manuscript.
Funding Nordic Cancer Union funded the NOCCA project. The work by AF, GBr, SC, GBi, FSV and SM was partially supported by internal funds of the Department of Medical and Surgical Sciences and the Department of Experimental, Diagnostic, and Specialty Medicine of the University of Bologna.
Competing interests None declared.
Ethics approval The NOCCA study has been approved by the ethical committees and the data inspection boards in each of the Nordic countries.
Provenance and peer review Not commissioned; externally peer reviewed.
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