Ask any seasoned lawyer how he or she plans to defend their next asbestos mesothelioma case and you are very unlikely to hear that general causation will be at the heart of their strategy. In other words, there seems to be a tacit acceptance that asbestos exposure in some form was a cause of the injury. And yet, when queried about the percentage of mesothelioma cases in which asbestos exposure played a role, most scientists and lawyers will quote rates of 80 – 90%. While that rate is extremely high, it is not 100%. That leaves 10 – 20% of cases where asbestos can be legitimately questioned as the cause of a mesothelioma injury.
These non-asbestos-induced mesotheliomas are evident when one looks at the secular trends of asbestos exposure juxtaposed on the rate of mesothelioma cases. A recent White Paper authored by Bertram Price of KCIC makes this point quite strongly using a secular time trend analysis. A figure from the paper demonstrates that despite plummeting asbestos exposure rates, mesothelioma rates in men and woman has remained remarkably steady. Price concludes from the data he reviewed that “…55% of all mesothelioma cases diagnosed in the U.S. were background cases; 37% of all male cases were background cases; and approximately 99% of all female cases were background cases.” While these estimates sound extreme, they are certainly noteworthy.
The steady rate of mesothelioma was confirmed in work by Nathan Associates (formerly Gnarus Advisors) in which they analyzed the latest federal data on mesothelioma diagnoses from cancer registries in the US, most notably the Surveillance, Epidemiology, and End Results (“SEER”) Program of the National Cancer Institute. While the SEER data reveal small decreases in the rate of mesothelioma diagnosis from 2014 to 2015, the decline was very small (from 0.924 in 2014 to 0.881 in 2015). Furthermore, the diagnosis rates for males increased and the diagnosis rates for females decreased. Finally, the report concludes that the rates of mesothelioma appear consistently stratified and stable by age cohort (as set forth in the following chart from the report).
To be sure, the evidence linking moderate to high doses of amphibole asbestos to mesothelioma is overwhelming. But that doesn’t mean these exposures are the only cause of mesothelioma. As the secular trend data suggests, it is quite reasonable to conclude that there are other factors that play a causal role in the induction of this disease. The scientific evidence linking non-asbestos factors to mesothelioma was recently summarized in a very recent paper by Richard Attanoos and colleagues in which they review factors like non-asbestos minerals (e.g., erionite), radiation, chronic inflammation, simian virus 40, and genomic factors (e.g., BAP1 cancer predisposition syndrome).
As we have emphasized in our past posts and in our consulting work for legal clients, cancer is a disease of the genome and mesothelioma is no exception. Recent studies have shown that significant portions of patients with malignant mesothelioma and uveal melanoma carry specific germline mutations that appear to be driving those cancers.
So, what do these genomic data mean for the defense of asbestos cases?
It means that in some individuals, mesothelioma is caused by specific genetic driver mutations. A recent paper titled Pathogenic Germline Variants in 10,389 Adult Cancers estimated that up to 9% of individuals are likely to carry specific mutations that drive mesothelioma. It is notable that this collaboration of 75 cancer researchers from the most prestigious institutions in the country list mesothelioma right along with over 30 other cancer types, making no mention of asbestos in the paper. Indeed, recent studies using high quality fiber burden analysis (including state-of-the-art scanning electron microscopy) demonstrate that a subset of mesothelioma cases have no demonstrable evidence of asbestos exposure.
As asbestos exposure rates continue to fall, and legal filings continue to pour in, genomics will be a powerful tool to demonstrate that a subset of mesothelioma cases can readily be identified and explained by specific genetic mutations and other factors.
Also, don’t forget to check out my recent blog post on recognizing legal cases where a genetic defense will be most beneficial.
Download a complimentary copy of the slides from my talk at the recent ACI Asbestos Conference entitled: “The Meso Gene”: Evaluating Predispositions to Certain Types of Cancer.
DOWNLOAD "THE MESO GENE" SLIDES
These slides on genetic factors related to mesothelioma are from a talk I gave at the recent ACI Asbestos conference.