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Article Abstract
Trying to use clinical trial data as a beacon to guide the use of new drugs in clinical practice can lead to errant expectations. Consider the story of the police officer who encountered a man looking for something near a street light after dark:

"What are you doing?" asked the police officer.
"Looking for the coin I dropped a little while ago down the street," replied the man.
"Why are you looking here instead of down the street where you dropped it?" queried the police officer.
"Because this is where the light is shining," answered the man.

Just because the light of research shines on a population of patients in a clinical trial doesn’ t always mean it will illuminate patients in clinical practice. Why is this so?