Does Medical Research Help Us Make Better Clinical Decisions?

Andrew J. Vickers, PhD

Disclosures

November 16, 2007

In This Article

What Do Clinical Trial Results Mean?

It might be a bit weird hearing this from a statistician, but when I read clinical trial results I often have no idea what they mean. Here is some recent news from oncology: "Elantra" improves survival in metastatic liver cancer (or is "Elantra" a type of car? I forget: the names all seem to blend together after a time). Here is the summary of the trial results:

"Elantra" treatment was associated with a median survival of 11.9 months versus 8.5 months for controls ( P = .002). The hazard ratio was 0.70. Two-year survival was 26% for "Elantra" versus 15% for standard care.

Fairly standard stuff...and almost totally useless in the clinic. Let's start with the hazard ratio. A hazard ratio of 0.70 means that at any randomly chosen time, patients taking the drug have about a 30% lower chance of dying the next day than do the controls. This is just about as difficult to explain to a patient as the P value (for example, try telling the patient, "The probability of a dataset at least this extreme under the null hypothesis is .002."). Moreover, the hazard ratio cannot possibly help a patient make a decision about whether or not to use "Elantra." To understand why, we need to think about a field of statistics known as "decision analysis."

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