Embedding clinical trials in clinical practice: Harvesting experience and winnowing evidence

[...] phase 3 trials focus mainly on surrogate endpoints which can be reached within a reasonable time, and which seem logically to bear on the ultimate desired outcomes, although there is no guarantee that this will always or necessarily be so. [...] phase 3 trials include patients with strict selection and exclusion criteria, with the result that they form a sample that is not representative of all the patients in whom the drug may or could be used.