  The development of targeted therapies, which benefit only a subgroup of
patients treated for a given type of cancer, has been extremely attractive to
many investigators. Adaptive seamless phase II/III designs in oncology clinical
trials with interim analyses for subpopulation selection could be used if
pre-defined biomarker hypothesis exists. We consider the interim analysis using
time-to-event endpoints, e.g., overall survival (OS) and progression-free
survival (PFS), to identify whether the whole population or only the
biomarker-positive population should be continued into the subsequent stage,
whereas a final decision is based on OS data. In this paper, we propose the
interim decision-making strategies in adaptive designs with correlated
endpoints, considering post-progression survival (PPS) magnitudes. In our
approach, the interim decision is made on the basis of predictive power, by
incorporating information on OS as well as PFS. We consider PFS data only in
making interim decision in order to supplement the immature OS data. Simulation
studies assuming a targeted therapy show that our interim decision procedure
performs well in terms of selecting the proper population, especially under a
scenario in which PPS affects the translation of the benefit from PFS to OS.
