Methods and Applications of Statistics in Clinical Trials, Volume 2: Planning, Analysis, and Inferential Methods

Chapter 4

Bandit Processes and Response-Adaptive Clinical Trials: The Art of Exploration Versus Exploitation

Xikui Wang

4.1 Introduction

Statistics show that the global life expectancy was 46 years in 1950 [17] and increased to 61 years in 1980 and to 67 years in 1998 [22]. On its web page, the World Health Organization [23] indicates that the average life expectancy at birth of the global population in 2011 was 70 years. We now live longer and better than ever before. Most of the gains have occurred in low- and middle-income countries and are attributed to improved nutrition and sanitation and improved public health infrastructure. Another important cause is of course the advancement, in medicine that have helped to improve both the mortality and morbidity of our lives. Clinical trials, as part of the mainstream clinical research, have significantly impacted on our lives because they provide the most reliable and efficient method to evaluate the effectiveness of new medical interventions.

Clinical trials are controlled experiments on human subjects and so involve the paramount issues of collective ethics and individual ethics. They also require that randomization be used as an indispensable element of the planned experiment. Challenges to clinical trials are often characterized by complex ethical and methodological issues. We face a delicate balance between minimizing biases of treatment comparison (in order to acquire evidence-based scientific knowledge) and maximizing ethics ...