_Lecture notes_phaseiii

_Lecture notes_phaseiii - Phase III Clinical Trials: Design...

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Phase III Clinical Trials: Design and Analysis Considerations Phase III trials are the large-scale comparative trials most of us have in mind when we think of clinical trials. They typically feature: Concurrent comparison with best available treatment, sometimes a placebo. Randomized assignment to treatment. Objective evaluation of response: By objective endpoints if possible, Otherwise by blinding or masking of participants and evaluators. Pre-planned analysis. Usually two-sided hypotheses, not one-sided. (Why?) Other features that may complicate the statistician’s job: More than two treatment arms. Unbalanced assignment to treatment. Need to block by site or by patient characteristics. Non-compliance, drop-out. Interim analyses. Testing for noninferiority instead of improvement over standard. More than one outcome measure. Cluster randomization. An interesting historical example: the 1954 polio vaccine trial. The heart of the study was a randomized, double-blind placebo-controlled trial in which about 200,000 children got active Salk vaccine and 200,000 got placebo. Among those who got vaccine, 57 got polio, total, for a rate of 28 per 100,000. Among those who got placebo, 142 got polio, for a rate of 71 per 100,000. This is a statistically significant difference. The rate for children whose parents declined consent was 54 per 100,000. This seems like a striking result. Could we have gotten by without placebo control? The initial study plan was to have an area where 2nd graders got vaccinated but 1st and 3rd graders did not, and to use the 1st and 3rd grade as a control group. In fact this was done, with 222,000 children in grade 2 in a different area vaccinated, another 124,000 in grade 2 whose parents did not consent, and a total of 725,000 unvaccinated 1st and 3rd grade controls. The polio rate per 100,000 in the vaccinated 2nd graders was 25 per
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This note was uploaded on 12/30/2010 for the course BST 252 taught by Professor Tsodikov during the Winter '06 term at UC Davis.

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_Lecture notes_phaseiii - Phase III Clinical Trials: Design...

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