A Minnesota appeals court recently affirmed summary judgment for defendants in a suit by a woman who alleged hormone replacement drugs caused her breast cancer. Zandi v. Wyeth, 2009 WL 2151141 (Minn.App.)
Plaintiff alleged that between approximately 1981 and 2001, she ingested hormone-replacement-therapy (HRT) drugs manufactured, designed, packaged, marketed, and distributed by defendants. In November 2001, Zandi was diagnosed with “hormone-dependent breast cancer.” She contended that the HRT drugs caused her cancer. She brought claims for negligence, strict liability, breach of implied warranty, breach of ex-press warranty, fraud, misrepresentation, and violation of the Minnesota fraudulent advertising act, the Minnesota Prevention of Consumer Fraud Act, and the Minnesota Uniform Deceptive Trade Practices Act.
The trial court found that plaintiff’s specific causation evidence did not satisfy Minnesota’s standard for admissibility of expert testimony. Zandi offered testimony from Dr. Lester Layfield and Dr. Gail Bender to prove that HRT drugs caused her cancer. Minnesota courts use the Frye standard to determine the admissibility of novel scientific evidence. Goeb v. Tharaldson, 615 N.W.2d 800, 814 (Minn.2000). Under Minnesota’s version of this standard, the proponent of scientific evidence must establish that the scientific theory is generally accepted in the relevant medical or scientific community and that the principles and methodology used are reliable. McDonough v. Allina Health Sys., 685 N.W.2d 688, 694 (Minn.App.2004). When novel scientific evidence is offered, (1) the trial court must determine whether it is generally accepted in the relevant scientific community; (2) the particular scientific evidence in each case must be shown to have foundational reliability.
Zandi’s claims were based on the following propositions: 1) it is generally accepted that HRT causes hormone-dependent breast cancer, and 2) there is a generally accepted method of diagnosing the cause of hormone-dependent breast cancer in an individual. The appellate issues revolved around the second. Defendants alleged that even if one assumes the relevant scientific community generally accepts that HRT causes hormone-dependent breast cancer, Zandi had failed to establish that the relevant scientific community generally agrees that there is a method of diagnosing the cause of breast cancer in a particular person.
Plaintiff’s experts based their specific causation opinions on epidemiological studies and differential diagnosis. But the science of epidemiology does not address the cause of an individual’s disease. Epidemiology is concerned with the incidence of disease in populations and does not address the question of cause of an individual’s disease. Epidemiology has its limits at the point where an inference is made that the relationship between an agent and a disease is causal (general causation) and where magnitude of excess risk attributed to the agent has been determined; that is, epidemiology addresses whether an agent can cause disease, not whether an agent did cause a specific plaintiff’s disease. See Green et al., Reference Guide on Epidemiology, in Reference Manual on Scientific Evidence 333, 381-82 (Fed.Jud.Ctr.2d ed.2000).
Plaintiff’s experts also relied on differential diagnosis. As used by plaintiffs, differential diagnosis adopts a process of elimination to identify cause; it seeks to eliminates the possibility of competing causes or confounding factors. Goeb, 615 N.W.2d at 815. In performing a differential diagnosis, a physician begins by ruling in all scientifically plausible causes of the patient’s injury. The physician then rules out the least plausible causes of injury until the most likely cause remains. Yet, breast cancer does not lend itself to such a differential diagnosis because the scientific community has not accepted that breast cancer has a limited number of discrete and recognized possible causes such that ruling out one cause would implicate another. For differential diagnosis to be sufficiently reliable to prove causation, the diagnostician should rule out all other hypotheses, or at least explain why the other conceivable causes are excludable.
Additional risk factors that plaintiff failed to adequately account for here included family history. Indeed, plaintiff’s experts suggested that it is possible to conduct a reliable differential diagnosis without ruling out other hypotheses.
On this record, the court said, “We conclude that there is not a method of diagnosing the specific cause of a particular woman’s breast cancer that is generally accepted in the relevant scientific community. This reality leaves Zandi without a legally sufficient ability to prove specific causation.”