Chapter 5. Design of Phase III Trials

  1. Allan Hackshaw Deputy Director1,2

Published Online: 29 APR 2009

DOI: 10.1002/9781444311723.ch5

A Concise Guide to Clinical Trials

A Concise Guide to Clinical Trials

How to Cite

Hackshaw, A. (2009) Design of Phase III Trials, in A Concise Guide to Clinical Trials, Wiley-Blackwell, Oxford, UK. doi: 10.1002/9781444311723.ch5

Author Information

  1. 1

    Cancer Research, UK

  2. 2

    UCL Cancer Trials Centre, UK

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 10 APR 2009

ISBN Information

Print ISBN: 9781405167741

Online ISBN: 9781444311723



  • phase III study – efficacy or safety, or both;
  • common efficacy endpoints – mortality, occurrence of disease of interest, further advancement of a disease being treated, cure or relief of chronic symptoms;
  • bioequivalence drug trials – two forms of the same drug produced using a new method or a different formulation;
  • parallel groups: each group of subjects receives only one intervention;
  • split-person design – to administer two interventions at the same time;
  • split-mouth design


This chapter contains sections titled:

  • Objectives of phase III trials

  • Types of phase III trials

  • Choosing outcome measures

  • Composite outcome measures

  • Having several outcome measures (multiple endpoints)

  • Fundamental information needed to estimate sample size

  • Method of sample-size calculation

  • Examples of sample-size calculations

  • The importance of having large enough trials, and specifying realistic effect sizes

  • Reasons for increasing the sample size

  • Other considerations in designing phase III trials

  • Summary

  • References