Causation Of Malignant Mesothelioma Research Articles

Chronological trends in the causation of malignant mesothelioma: Fiber burden analysis of 619 cases over four decades

Malignant mesothelioma is a relatively rare malignancy with a strong association with prior asbestos exposure. A percentage of cases is not related to asbestos, and fiber analysis of lung tissue is a useful methodology for identifying idiopathic or spontaneous cases. We have performed fiber analyses in more than 600 cases of mesothelioma over the past four decades and were interested in looking for trends in terms of fiber types and concentrations as well as percentages of cases not related to asbestos. Demographic information was also considered including patient age, gender, and tumor location (pleural vs. peritoneal). The histologic pattern of the tumor and the presence or absence of pleural plaques or asbestosis were noted. Fiber analysis was performed in 619 cases, using the sodium hypochlorite technique for digestion of lung tissue samples. Asbestos bodies were counted by light microscopy (LM) and coated and uncoated fibers by scanning electron microscopy (EM). The results were stratified over four decades. Trends that were observed included increasing patient age, increasing percentage of women, increasing percentage of peritoneal cases, and increasing percentage of epithelial histological type. There was a decreasing trend in the percentage of patients with concomitant asbestosis (p < 0.001). The percentage of cases with an elevated lung asbestos content decreased from 90.5% in the 1980s to 54.1% in the 2010s (p < 0.001). This trend also held when the analysis was limited to 490 cases of pleural mesothelioma in men (91.8% in the 1980s vs. 65.1% in the 2010s). There was a decrease in the median asbestos body count by LM from 1390 asbestos bodies per gram of wet lung in the 1980s to 38 AB/gm in the 2010s. Similar trends were observed for each of the asbestos fiber types as detected by EM. We conclude that there has been a progressive decrease in lung fiber content of mesothelioma patients during the past four decades, with an increasing percentage of cases not related to asbestos and an increase in median patient age.

Re: Comments on the causation of malignant mesothelioma: Rebutting the false concept that recent exposures to asbestos do not contribute to causation of mesothelioma.

BACKGROUND European asbestos manufacturers and their expert witnesses have advanced the claim that recent exposures to asbestos are not of significance in the causation of malignant mesothelioma. They argue that in cases of prolonged exposure to asbestos only the earliest exposures contribute to mesothelioma induction. METHODS The Collegium Ramazzini examined this claim and compared it with the findings of the Epidemiology and Public Health Working Group of the Second Italian Consensus Conference on Pleural Mesothelioma. This independent Working Group noted that earlier exposures are more effective in inducing mesothelioma, but that subsequent exposures also contribute and cannot be excluded. They found convincing evidence to support the conclusion that mesothelioma incidence is proportional to cumulative asbestos exposure. CONCLUSION The Collegium Ramazzini concludes that risk of malignant mesothelioma is proportional to cumulative exposure to asbestos in which all exposures - early as well as late - contribute to the totality of risk. The Collegium Ramazzini rejects as false and scientifically unfounded the notion that only the earliest exposures to asbestos contribute to mesothelioma induction.

Comments on the Causation of Malignant Mesothelioma: Rebutting the False Concept That Recent Exposures to Asbestos Do Not Contribute to Causation of Mesothelioma

BackgroundEuropean asbestos manufacturers and their expert witnesses have advanced the claim that recent exposures to asbestos are not of significance in the causation of malignant mesothelioma. They argue that in cases of prolonged exposure to asbestos only the earliest exposures contribute to mesothelioma induction. MethodsThe Collegium Ramazzini examined this claim and compared it with the findings of the Epidemiology and Public Health Working Group of the Second Italian Consensus Conference on Pleural Mesothelioma. This independent Working Group noted that earlier exposures are more effective in inducing mesothelioma, but that subsequent exposures also contribute and cannot be excluded. They found convincing evidence to support the conclusion that mesothelioma incidence is proportional to cumulative asbestos exposure. ConclusionThe Collegium Ramazzini concludes that risk of malignant mesothelioma is proportional to cumulative exposure to asbestos in which all exposures - early as well as late - contribute to the totality of risk. The Collegium Ramazzini rejects as false and scientifically unfounded the notion that only the earliest exposures to asbestos contribute to mesothelioma induction.

Comments on the causation of malignant mesothelioma: Rebutting the false concept that recent exposures to asbestos do not contribute to causation of mesothelioma.

BACKGROUND European asbestos manufacturers and their expert witnesses have advanced the claim that recent exposures to asbestos are not of significance in the causation of malignant mesothelioma. They argue that in cases of prolonged exposure to asbestos only the earliest exposures contribute to mesothelioma induction. METHODS The Collegium Ramazzini examined this claim and compared it with the findings of the Epidemiology and Public Health Working Group of the Second Italian Consensus Conference on Pleural Mesothelioma. This independent Working Group noted that earlier exposures are more effective in inducing mesothelioma, but that subsequent exposures also contribute and cannot be excluded. They found convincing evidence to support the conclusion that mesothelioma incidence is proportional to cumulative asbestos exposure. CONCLUSION The Collegium Ramazzini concludes that risk of malignant mesothelioma is proportional to cumulative exposure to asbestos in which all exposures - early as well as late - contribute to the totality of risk. The Collegium Ramazzini rejects as false and scientifically unfounded the notion that only the earliest exposures to asbestos contribute to mesothelioma induction.

Comments on the causation of malignant mesothelioma: rebutting the false concept that recent exposures to asbestos do not contribute to causation of mesothelioma.

Comments on the causation of malignant mesothelioma: rebutting the false concept that recent exposures to asbestos do not contribute to causation of mesothelioma.

Comments on the causation of malignant mesothelioma: rebutting the false concept that recent exposures to asbestos do not contribute to causation of mesothelioma.

The Collegium Ramazzini is an international scientific society that examines critical issues in occupational and environmental medicine with a view towards action to prevent disease and promote health. The Collegium derives its name from Bernardino Ramazzini, the father of occupational medicine, a professor of medicine of the Universities of Modena and Padua in the late 1600s and the early 1700s. The Collegium is comprised of 180 physicians and scientists from 35 countries, each of whom is elected to membership. The Collegium is independent of commercial interests.

Mesothelioma in patients with nonoccupational asbestos exposure

The specific parameters of nonoccupational asbestos exposures (NOAE) that can distinguish an idiopathic from an asbestos-caused malignant mesothelioma (MM) are controversial. A systematic literature review yielded 1028 cases with this putative association. Only 287 of those reports had a defined single exposure to a household, building occupant, or neighborhood/community asbestos source. The available "evidence" was used to develop semiarbitrary evidence-based causation guideline rules for the assessment of putative associations between MM and NOAE. The rules are classified into class A (tissue burden analysis shows asbestos body counts or fiber counts in lung tissues comparable to MM caused by occupational exposure to asbestos) and classes B to D based on whether certain combinations of NOAE features and MM (evidence) have been described in over 15% (class B), 5% to 15% (class C), and less than 5% (class D) of the patients reviewed. The proposed 4 classes of evidence-based causation guidelines provide a semiarbitrary framework to evaluate the causation of individual MM patients by NOAE based on decreasing levels of currently available evidence. The neoplasms in classes A to C patients are probably caused by NOAE, with decreasing weight of evidence in the 3 groups. There is minimal evidence to support the causation of MM by NOAE in class D patients. There is no evidence or only anecdotal evidence to support a causal association between MM and NOAE in individuals who cannot be classified into any of the 4 classes. Future studies are needed to provide more comprehensive data regarding the association between MM and NOAE.

Current controversies regarding the role of asbestos exposure in the causation of malignant mesothelioma: the need for an evidence-based approach to develop medicolegal guidelines.

Asbestos is a group of fibrous silicate minerals that includes two mineralogic groups: amphiboles and serpentines. While the carcinogenic role of amphiboles (eg, crocidolite and amosite) is well established, medical "experts" that tend to strongly advocate their views currently argue in medicolegal cases multiple specific issues regarding the carcinogenicity of asbestos fibers. For example, it is controversial whether chrysotile causes malignant mesothelioma (MM); what are the specific carcinogenic thresholds for amphiboles and chrysotile; what occupations are truly at risk to develop MM as a result of asbestos exposure; what is the role of chrysotile in the development of peritoneal MM; how to assign causation in individuals exposed to multiple industrial products containing variable concentrations of various asbestos fibers; and, what criteria should be used to accept causation in household exposure cases and others. The causation criteria currently acceptable in U.S. courts are surprisingly flexible and subject to variable interpretation by medical "experts." At a time where thousands of individuals are claiming causation of MM by asbestos exposure, there is a need to develop more specific causation guidelines based on scientific evidence. Evidence-based medicine has been proposed as a new approach to the study, teaching, and the practice of medicine and has been used as a process of systematically reviewing the relevant studies in the literature to assess their scientific validity and development of guidelines. This article summarizes some of the current controversies regarding the role of asbestos exposure in the causation of MM and suggests the need for future evidence-based medicine-type studies to develop causation guidelines that could be used consistently during litigation.