This year juries returned verdicts totaling nearly $200 million in three Missouri cases claiming that ovarian cancers is caused by using talcum powder products. By contrast, in September a New Jersey Superior Court excluded expert opinions offered to support such claims and granted defense motions for summary judgment in two pending cases.
What scientific evidence is there concerning the causal connection, or lack of it, between talc use and ovarian cancer?
In the New Jersey cases, the court held a nine day evidentiary hearing and considered briefs and scientific literature submitted by the parties. It focused on the opinions of Dr. Graham Colditz and Dr. Daniel Cramer, the plaintiffs’ principal causation experts, stating the question as follows: “Have Plaintiffs shown that their experts’ theories of causation are sufficiently reliable as being based on a sound, adequately-founded scientific methodology?” Both experts relied on case-control epidemiological studies to support their opinions, and the court proceeded to examine their methodology.
“Epidemiologic studies attempt to identify agents that are associated with an increased risk of disease. Thus, the first question an epidemiologist must ask is whether or not an association exists between exposure to a substance and a particular disease,” the court said. The strength of an association in an epidemiological study is commonly measured by relative risk. A risk ratio of 1.0 shows that there is no association, while a risk ratio of 2.0 means that the risk is double that of mere chance. Citing the Reference Manual on Scientific Evidence, the court stated, “An association is not equivalent to causation,” and said that determining whether an association is causal requires assessment of a study’s design and implementation and how it fits with other scientific knowledge.
The court concluded that neither expert was able to provide a plausible biologic explanation for how talc could cause ovarian cancer. They theorized that talc causes inflammation of the ovaries, but could point to no evidence supporting this theory. Moreover, neither of the plaintiffs experienced such inflammation or was diagnosed with the type of cancer the experts said was most commonly associated with talc use. The experts made no effort to address studies showing that talc actually inhibits blood vessel growth, which is an anti-cancer property, or to respond to a Food and Drug Administration finding of no “cogent biological mechanism by which talc might lead to ovarian cancer.” Dr. Colditz admitted that he knew of no scientific study purporting to explain the biological process whereby talc causes cancer, and his own prior writings found “little support for any substantial association” between talc use and ovarian cancer.
The Reference Manual states that case-control studies are inherently less reliable than large scale cohort studies of exposed and unexposed persons. Dr. Cramer relied on case-control studies he conducted beginning in 1982 to show an association between talc use and ovarian cancer. None of them showed a risk ratio greater than 1.29, which he acknowledged was “weak.” He made no effort to distinguish or explain much larger and more reliable cohort studies which showed no such association.
Nor did Dr. Cramer make any effort to explain how talc is capable of causing ovarian cancer in any person (general causation) or in either of the plaintiffs (specific causation). The court noted that Dr. Cramer never stated an opinion in his peer-reviewed articles that talc causes ovarian cancer; in fact, he expressly disclaimed such an opinion in a 2007 study.
Yet Dr. Cramer relied solely on his own case control studies to establish both general and specific causation in the litigation “by the numbers,” as the court put it. The court noted the caveat in the Reference Manual that, “specific causation is beyond the domain of the science of epidemiology.” And Dr. Cramer made no effort to account for the fact that both plaintiffs had significant independent risk factors for developing ovarian cancer.
The court concluded, “Though both Plaintiffs’ experts are eminently qualified, their areas of scientific inquiry, reasoning and methodology are slanted away from objective science and toward advocacy.” Accordingly, it granted defense motions to bar their opinions and for summary judgment.
Like the Missouri jury verdicts, the New Jersey decision will ultimately be determined on appeal. However, the opinion demonstrates the type of careful examination that Courts should make of expert opinions in complex product liability cases.