Optimal Sample Size and Go/No-Go Decision Based on Probability of Success

• Activity Number: 580
• Type: Contributed
• Date/Time: Wednesday, August 3, 2011 : 2:00 PM to 3:50 PM
• Sponsor: Biopharmaceutical Section
• Author(s): Kaihong Jiang*+
• Companies: sanofi-aventis
• Keywords: Go/No-go decision ; Probability of success ; Program-wise planning ; Optimal sample size ; Bayesian ; Phase II-III

Abstract

In the course of a phase II/III clinical program, one faces a series of sample size determination (SSD) and decision problems: the simultaneous SSD for both phase II and III trials at the program planning stage, the go/no-go decisions after phase II data is observed, and the SSD of phase III trials incorporating phase II data. Conventionally, SSD are on trial-by-trial basis and independent of one another, and go/no-go decisions are made based on statistics, eg., p-values, that are ambiguous at times for decision making. In a combined Bayesian and frequentist framework, a probability of success (POS) function is proposed to allow an integrated approach to the SSD and go/no-go decision problems for a phase II/III program with a normal variable. For the first time, optimal sample sizes can be determined simultaneously for a phase II/III program based on the proposed POS function. As the POS function includes the conventional power function as a special case, it enjoys broader applications in trial planning than the power-based procedures, including SSD of phase II trials and that of phase III trials incorporating phase II data - neither can be handled readily by conventional methods.