Article Text
Abstract
Objectives Models based on the multistage theory of cancer predict that rates of malignant mesothelioma continuously increase with time since first exposure (TSFE) to asbestos, even after the end of external exposure. However, recent epidemiological studies suggest that mesothelioma rates level off many years after first exposure to asbestos. A gradual clearance of asbestos from the lungs has been suggested as a possible explanation for this phenomenon. We analysed long-term trends of pleural and peritoneal cancer mortality in subjects exposed to asbestos to evaluate whether such trends were consistent with the clearance hypothesis.
Methods We used data from a pool of 43 Italian asbestos cohorts (51 801 subjects). The role of asbestos clearance was explored using the traditional mesothelioma multistage model, generalised to include a term representing elimination of fibres over time.
Results Rates of pleural cancer increased until 40 years of TSFE, but remained stable thereafter. On the other hand, we observed a monotonic increase of peritoneal cancer with TSFE. The model taking into account asbestos clearance fitted the data better than the traditional one for pleural (p=0.004) but not for peritoneal (p=0.09) cancer.
Conclusions Rates of pleural cancer do not increase indefinitely after the exposure to asbestos, but eventually reach a plateau. This trend is well described by a model accounting for a gradual elimination of the asbestos fibres. These results are relevant for the prediction of future rates of mesothelioma and in asbestos litigations.
- epidemiology
- mesothelioma
- asbestos
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Footnotes
Collaborators Maria Nicoletta Ballarin (previously: Mesothelioma Register of the Veneto Region, Local Health Unit, Padua, Italy), Lucia Bisceglia (Regional Health Agency of Puglia, Bari, Italy), Carol Brentisci (Unit of Cancer Epidemiology, CPO Piemonte and University of Turin, Turin, Italy), Barbara Cortini (Occupational and Environmental Epidemiology Unit - Istituto per lo Studio, la Prevenzione e la Rete oncologica (ISPRO), Florence, Italy), Stefano Mattioli (Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy), Manuela Gangemi (Unit of Cancer Epidemiology, CPO Piemonte and University of Turin, Turin, Italy), Francesco Gioffrè (previously: Mesothelioma Register of the Veneto Region, Local Health Unit, Padua, Italy), Patrizia Legittimo (formerly at Unit of Occupational Medicine, S Orsola-Malpighi University Hospital, Bologna, Italy), Lucia Mangone (Epidemiology Unit, AUSL Reggio Emilia and IRCCS, Reggio Emilia, Italy), Francesco Marinelli (Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy), Pasqualina Marinilli (Department of Public Health, Prevention and Security Area Work Environments, Local Health Authority, Bologna, Italy), Anna Maria Nannavecchia (Regional Health Agency of Puglia, Bari, Italy), Chiara Panato (previously: Mesothelioma Register of the Veneto Region, Local Health Unit, Padua, Italy), Francesca Roncaglia (Epidemiology Unit, AUSL Reggio Emilia and IRCCS, Reggio Emilia, Italy), Cinzia Storchi (Occupational Hygienist; formerly: Regional Agency for Protection, Environment and Energy Emilia-Romagna, Provincial Office of Reggio Emilia, Italy), Antonella Stura (Unit of Cancer Epidemiology, CPO Piemonte and University of Turin, Turin, Italy), Massimo Vicentini (Occupational Hygienist; formerly: Regional Agency for Protection, Environment and Energy Emilia-Romagna, Provincial Office of Reggio Emilia, Italy), Simona Verdi (Istituto per lo Studio, la Prevenzione e la Rete oncologica (ISPRO), Florence, Italy).
Contributors FB-A: study design, planning and overview of data analysis, and drafting and critical revision of the article. DF: design of the study, data management, design and conduct of data analysis, and critical revision of the article. AA, MM, PP, AP, FC, SC, AB, LA, ER, FL, OS, CS, SM, EO, LM, GG, VB, VP, EM, EC: design of the study, conduct of the study and critical revision of the article. SS: exposure assessment and critical revision of the article. PG: design of the study and of data analysis and critical revision of the article. ST: data management and critical revision of the article. AR, TC: data management, data analysis and critical revision of the article. AM: design of the study, incidence data collection coordination and critical revision of the article. DM: design of the study, evaluation of exposure information and critical revision of the article. RP: design of the study, overview of mortality data analyses and critical revision of the article. CM: PI of the study, overview of the study and critical revision of the article.
Funding The project was partially funded by the Italian National Institute of Health - Istituto Superiore di Sanità (ISS). Asbestos Project - Ricerca corrente 2012: Progetto Amianto. The 'Casaralta' cohort study was partially funded by the Regional Government of Emilia Romagna (Resolution No 6 of the Regional Council of 18/12/2006).
Competing interests SM served as expert witness for the judge, the public prosecutor and the defendant’s attorneys in court trials regarding asbestos-related diseases. CM and SS served as expert witnesses for the judge and the public prosecutor in court trials regarding asbestos-related diseases. AA, FB-A, PL, EM, LMi, DM and EO served as expert witnesses for the public prosecutor in court trials regarding asbestos-related diseases. LMa conducted negotiations and stipulated contracts representing the Italian Association of Cancer Registries (AIRTUM) for the preparation and publication of specific reports on the epidemiology of tumour pathologies with MSD, Lilly and Sanofi. All other authors declare they have no actual or potential competing financial interests.
Patient consent for publication Not required.
Ethics approval The study was approved by the University of Eastern Piedmont Ethical Review Board (Authorisation CE112/13, 12 July 2013) and to the corresponding boards of participating institutions.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No additional data are available.