Background The primary objective of phase II cancer clinical trials is to determine whether a
new regimen has sufficient activity to warrant further study, with activity generally defined as
tumor shrinkage. However, oncology drug development has been limited by high rates of
failure (lack of efficacy) in subsequent phase III testing. This high failure rate may reflect the
process by which antineoplastic agents are usually evaluated in phase II trials, ie, via single-
arm studies in which the primary efficacy measure is the proportion of patients who achieve …

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