ABSTRACT
As indicated early in Chapter 1, an adaptive design is a design that allows
adaptations or modifications to some aspects of a trial after its initiation
without undermining the validity and integrity of the trial. The adapta-
tions may include, but are not limited to, sample-size reestimation, early
stopping for efficacy or futility, response-adaptive randomization, and drop-
ping inferior treatment groups. Adaptive designs usually require unblinding
data and invoke a dependent sampling procedure. Therefore, theory behind
adaptive design is much more complicated than that behind classical design.
Validity and integrity have been strongly debated from statistical, opera-
tional, and regulatory perspectives during the past several years. However,
despite different views, most scholars and practitioners believe that adap-
tive design could prove to be an efficient tool for drug development if used
properly. The issues of validity and integrity will be discussed in depth in
Chapter 28.
